Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2018	Jan. 31, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Trading Symbol	FGEN
Entity Registrant Name	FIBROGEN INC
Entity Central Index Key	0000921299
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Shell Company	false
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		85,562,391
Entity Public Float			$ 3,548.1

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 89,258	$ 673,658
Short-term investments	532,144	62,060
Accounts receivable ($47,210 and $4,004 from a related party)	63,684	8,452
Prepaid expenses and other current assets	4,929	4,800
Total current assets	690,015	748,970
Restricted time deposits	4,145	5,181
Long-term investments	55,820	10,506
Property and equipment, net	127,198	129,476
Other assets	3,420	4,517
Total assets	880,598	898,650
Current liabilities:
Accounts payable	9,139	5,509
Accrued liabilities ($444 and $272 to a related party)	66,123	63,781
Deferred revenue	13,771	16,670
Total current liabilities	89,033	85,960
Long-term portion of lease financing obligations	97,157	97,763
Product development obligations	16,798	17,244
Deferred rent	3,038	3,657
Deferred revenue, net of current	136,109	138,241
Other long-term liabilities	9,993	8,047
Total liabilities	352,128	350,912
Commitments and Contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value; 125,000 shares authorized; no shares issued and outstanding at December 31, 2018 and December 31, 2017	0	0
Common stock, $0.01 par value; 225,000 shares authorized at December 31, 2018 and December 31, 2017; 85,432 and 82,498 shares issued and outstanding at December 31, 2018 and December 31, 2017	854	825
Additional paid-in capital	1,226,453	1,160,094
Accumulated other comprehensive loss	(2,281)	(1,795)
Accumulated deficit	(715,827)	(630,657)
Total stockholders’ equity	509,199	528,467
Non-controlling interests	19,271	19,271
Total equity	528,470	547,738
Total liabilities, stockholders’ equity and non-controlling interests	$ 880,598	$ 898,650

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Accounts receivable from related party	$ 47,210	$ 4,004
Accrued liabilities to related party	$ 444	$ 272
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	125,000,000	125,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	225,000,000	225,000,000
Common stock, shares issued	85,432,000	82,498,000
Common stock, shares outstanding	85,432,000	82,498,000

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Total revenue	$ 212,958	$ 130,996	$ 183,189
Operating expenses:
Research and development	235,839	196,517	187,206
General and administrative	63,812	51,760	46,025
Total operating expenses	299,651	248,277	233,231
Loss from operations	(86,693)	(117,281)	(50,042)
Interest and other, net
Interest expense	(10,991)	(9,706)	(10,725)
Interest income and other, net	11,568	6,433	2,628
Total interest and other, net	577	(3,273)	(8,097)
Loss before income taxes	(86,116)	(120,554)	(58,139)
Provision for (benefit from) income taxes	304	321	(71)
Net loss	$ (86,420)	$ (120,875)	$ (58,068)
Net loss per share - basic and diluted	$ (1.03)	$ (1.66)	$ (0.93)
Weighted average number of common shares used to calculate net loss per share - basic and diluted	84,062	72,987	62,744
License Revenue [Member]
Revenue:
Total revenue	$ 22,269	$ 9,933	$ 50,607
Development and Other Revenue [Member]
Revenue:
Total revenue	125,913	121,063	132,582
Product Revenue [Member]
Revenue:
Total revenue	$ 64,776	$ 0	$ 0

Consolidated Statements of Operations (Parenthetical) - Astellas Agreement [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
License and milestone revenue from a related party	$ 14,323	$ 0	$ 9,548
Collaboration services and other revenue from a related party	20,903	20,111	21,775
Product revenue from a related party	$ 64,776	$ 0	$ 0

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (86,420)	$ (120,875)	$ (58,068)
Other comprehensive income (loss):
Foreign currency translation adjustments	771	(2,022)	532
Available-for-sale investments:
Unrealized gain (loss) on investments, net of tax effect	(7)	1,259	140
Reclassification from accumulated other comprehensive loss	0	(72)	19
Net change in unrealized gain on available-for-sale investments	(7)	1,187	159
Other comprehensive income (loss), net of taxes	764	(835)	691
Comprehensive loss	$ (85,656)	$ (121,710)	$ (57,377)

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Noncontrolling Interests [Member]
Balance at Dec. 31, 2015	$ 153,173	$ 620	$ 586,647	$ (1,651)	$ (451,714)	$ 19,271
Balance, Shares at Dec. 31, 2015		61,985,079
Net loss	(58,068)	$ 0	0	0	(58,068)	0
Change in unrealized gain or loss on investments	159	0	0	159	0	0
Foreign currency translation adjustments	532	0	0	532	0	0
Shares issued from stock plans, net of payroll taxes paid	7,141	$ 17	7,124	0	0	0
Shares issued from stock plans, net of payroll taxes paid, Shares		1,660,759
Stock appreciation rights settled	0	$ 0	0	0	0	0
Stock appreciation rights settled, Shares		17,855
Stock-based compensation	32,132	$ 0	32,132	0	0	0
Warrants exercised	0	$ 0	0	0	0	0
Warrants exercised, Shares		1,591
Balance at Dec. 31, 2016	135,069	$ 637	625,903	(960)	(509,782)	19,271
Balance, Shares at Dec. 31, 2016		63,665,284
Net loss	(120,875)	$ 0	0	0	(120,875)	0
Change in unrealized gain or loss on investments	1,187	0	0	1,187	0	0
Foreign currency translation adjustments	(2,022)	0	0	(2,022)	0	0
Follow-on Offerings, net of underwriting discounts, commission and issuance costs	470,226	$ 144	470,082	0	0	0
Follow-on Offerings, net of underwriting discounts, commission and issuance costs, Shares		14,428,750
Shares issued from stock plans, net of payroll taxes paid	26,614	$ 44	26,570	0	0	0
Shares issued from stock plans, net of payroll taxes paid, Shares		4,404,094
Stock-based compensation	37,539	$ 0	37,539	0	0	0
Balance at Dec. 31, 2017	547,738	$ 825	1,160,094	(1,795)	(630,657)	19,271
Balance, Shares at Dec. 31, 2017		82,498,128
Impact of change inaccounting principle uponadoption of ASU 2016-01(Note 2) \| ASU 2016-01 [Member]	0	$ 0	0	(1,250)	1,250	0
Net loss	(86,420)	0	0	0	(86,420)	0
Change in unrealized gain or loss on investments	(7)	0	0	(7)	0	0
Foreign currency translation adjustments	771	0	0	771	0	0
Adjustment to issuance costs for Follow-on Offerings	11	0	11	0	0	0
Shares issued from stock plans, net of payroll taxes paid	14,235	$ 29	14,206	0	0	0
Shares issued from stock plans, net of payroll taxes paid, Shares		2,933,974
Stock-based compensation	52,142	$ 0	52,142	0	0	0
Balance at Dec. 31, 2018	$ 528,470	$ 854	$ 1,226,453	$ (2,281)	$ (715,827)	$ 19,271
Balance, Shares at Dec. 31, 2018		85,432,102

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net loss	$ (86,420)	$ (120,875)	$ (58,068)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation	6,562	6,099	6,040
Net amortization of premium and discount on investments	(42)	1,844	2,729
Unrealized loss on cash equivalents and short-term equity investments	1,120	2	0
Loss on disposal of property and equipment	53	3	0
Stock-based compensation	52,142	37,539	32,132
Realized foreign currency gain	(1,074)	0	0
Tax benefit on unrealized gain on available-for-sale securities	0	0	(211)
Realized gain on sales of available-for-sale securities	(87)	(143)	(37)
Changes in operating assets and liabilities:
Accounts receivable ($(43,206), $98 and $353 from related party)	(55,232)	1,996	4,957
Prepaid expenses and other current assets	(129)	(1,911)	1,099
Other assets	1,090	(2,365)	(136)
Accounts payable	3,630	(714)	(298)
Accrued liabilities ($172, $(1,343) and $(430) from related party)	5,606	9,196	2,965
Deferred revenue	(5,031)	174	13,225
Lease financing liability	32	1,023	814
Other long-term liabilities	1,636	1,619	1,897
Net cash provided by (used in) operating activities	(76,144)	(66,513)	7,108
Investing activities
Purchases of property and equipment	(8,020)	(8,500)	(1,252)
Proceeds from sale of property and equipment	184	5	0
Purchases of available-for-sale securities and term deposit	(576,880)	(169)	(9,041)
Proceeds from sales of available-for-sale securities	8,167	21,109	4,298
Proceeds from maturities of investments	54,426	57,421	12,617
Net cash provided by (used in) investing activities	(522,123)	69,866	6,622
Financing activities
Borrowings under capital lease obligations	49	0	0
Repayments of capital lease obligations	(6)	0	0
Repayments of lease liability	(403)	(403)	(403)
Proceeds from follow-on offerings, net of underwriting discounts and commission costs	0	471,205	0
Cash paid for payroll taxes on restricted stock unit releases	(15,612)	(8,296)	(2,740)
Proceeds from issuance of common stock	29,847	34,910	9,881
Payments of deferred offering costs	0	(944)	0
Net cash provided by financing activities	13,875	496,472	6,738
Effect of exchange rate change on cash and cash equivalents	(8)	51	(10)
Net increase (decrease) in cash and cash equivalents	(584,400)	499,876	20,458
Total cash and cash equivalents at beginning of period	673,658	173,782	153,324
Total cash and cash equivalents at end of period	89,258	673,658	173,782
Supplemental cash flow information:
Interest payments	218	255	295
Balance in accounts payable and accrued liabilities related to purchases of property and equipment	276	3,781	356
Deferred offering costs recorded in accounts payable and accrued liabilities	$ 24	$ 35	$ 0

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Cash Flows [Abstract]
Accounts receivable from related party	$ (43,206)	$ 98	$ 353
Accrued liabilities from related party	$ 172	$ (1,343)	$ (430)

The Company

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

The Company

1.	The Company

FibroGen, Inc. (“FibroGen” or the “Company”) was incorporated in 1993 in Delaware and is a leading biopharmaceutical company discovering and developing a pipeline of first-in-class therapeutics. The Company has applied its pioneering expertise in hypoxia-inducible factor (“HIF”) and connective tissue growth factor (“CTGF”) biology to develop innovative medicines for the treatment of anemia, fibrotic disease, and cancer. Roxadustat (FG-4592), the Company’s most advanced product candidate, is an oral small molecule inhibitor of HIF prolyl hydroxylase (“HIF-PH”) activity. Roxadustat has received approval of its New Drug Application (“NDA”) in anemia associated with chronic kidney disease (“CKD”) in dialysis-dependent patients from the National Medical Products Administration (“NMPA”) of the People’s Republic of China (“China”). In conjunction with our collaboration partners, we have completed the Phase 3 trials of roxadustat intended to support an NDA in the United States (“U.S.”) and a Marketing Authorization Application (“MAA”) in the European Union for the treatment of anemia in CKD. In collaboration with its partners AstraZeneca AB (“AstraZeneca”) and Astellas Pharma Inc. (“Astellas”), the Company is in the process of preparing the NDA for submission to the U.S. Food and Drug Administration (“FDA”) and MAAs for submission to the European Medicines Agency this year. Both the U.S. NDA and European MAA for roxadustat are expected to cover anemia associated with dialysis-dependent CKD and non-dialysis-dependent CKD. The Company is also in Phase 3 clinical development for the treatment of anemia associated with myelodysplastic syndromes (“MDS”). Pamrevlumab, a human monoclonal antibody that inhibits the activity of CTGF, is advancing towards Phase 3 clinical development for the treatment of idiopathic pulmonary fibrosis (“IPF”) and pancreatic cancer, and is currently in a Phase 2 trial for Duchenne muscular dystrophy (“DMD”).

On April 11, 2017, the Company closed a follow-on offering of its common stock. In this offering, the Company sold 5,228,750 shares of its common stock at a public offering price of $22.95 per share. Net proceeds from this offering were $115.1 million, after deducting underwriting discounts and commissions of $4.9 million. In addition, the offering expenses were approximately $0.6 million in total. On August 24, 2017, the Company completed another follow-on offering of its common stock. In this offering, the Company sold a total of 9,200,000 shares of its common stock at a public offering price of $40.75 per share. Net proceeds from this offering were $356.2 million, after deducting underwriting discounts and commissions of $18.7 million. In addition, the offering expenses were approximately $0.4 million in total.

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2.	Summary of Significant Accounting Policies

Basis of Presentation

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”). The consolidated financial statements include the accounts of the Company, its wholly owned subsidiaries and its majority-owned subsidiaries, FibroGen Europe and FibroGen China Anemia Holdings, Ltd. (“FibroGen China”). All inter-company transactions and balances have been eliminated in consolidation.

The Company operates in one segment — the discovery, development and commercialization of novel therapeutics to treat serious unmet medical needs.

Foreign Currency Translation

The reporting currency of the Company and its subsidiaries is the United States (“U.S.”) dollar. The functional currency of FibroGen Europe is the Euro. The assets and liabilities of FibroGen Europe are translated to U.S. dollars at exchange rates in effect at the balance sheet date. All income statement accounts are translated at monthly average exchange rates. Resulting foreign currency translation adjustments are recorded directly in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity.

The functional currency of FibroGen, Inc. and all other subsidiaries is the U.S. dollar. Accordingly, monetary assets and liabilities in the non-functional currency of these subsidiaries are remeasured using exchange rates in effect at the end of the period. Revenues and costs in local currency are remeasured using average exchange rates for the period, except for costs related to those balance sheet items that are remeasured using historical exchange rates. The resulting remeasurement gains and losses are included within interest income and other, net in the consolidated statements of operations as incurred and have not been material for all periods presented.

Use of Estimates

The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions include valuation and recognition of revenue, estimates of accruals related to clinical trial costs, valuation allowances for deferred tax assets, and valuation and recognition of stock-based compensation. On an ongoing basis, management reviews these estimates and assumptions. Changes in facts and circumstances may alter such estimates and actual results could differ from those estimates.

Concentration of Credit Risk and Other Risks and Uncertainties

The Company is subject to risks associated with concentration of credit for cash and cash equivalents. A portion of cash on hand is invested in a diversified portfolio of investment grade corporate bonds issued by U.S. corporations as rated investment grade corporate bonds. Any remaining cash is deposited with major financial institutions in the U.S., Finland, China and the Cayman Islands. At times, such deposits may be in excess of insured limits. The Company has not experienced any loss on its deposits of cash and cash equivalents. Included in current assets are significant balances of accounts receivable as follows:

	December 31,
	2018			2017
Astellas Pharma Inc. (“Astellas”)—Related party		74	%		47	%
AstraZeneca AB (“AstraZeneca”)		26	%		53	%

The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, rapid technological change, the results of clinical trials and the achievement of milestones, market acceptance of the Company’s product candidates, competition from other products and larger companies, protection of proprietary technology, strategic relationships and dependence on key individuals.

Cash, Cash Equivalents and Restricted Time Deposits

The Company considers all highly liquid investments with maturities of three months or less and that are used in the Company’s cash management activities at the date of purchase to be cash equivalents. Cash and cash equivalents include money market accounts, various deposit accounts, and money market funds. Restricted time deposits include an irrevocable standby letter of credit as security deposit for a long-term property lease with the Company’s landlord. Restricted time deposits as of December 31, 2018 and 2017 totaled $4.1 million and $5.2 million, respectively. As of December 31, 2018, a total of $21.9 million of the Company’s cash and cash equivalents is held outside of the U.S. in the Company’s foreign subsidiaries to be used primarily for the Company’s China operations.

Investments

The Company’s investments consist of available-for-sale debt investments, marketable equity investments, a term deposit and a certificate of deposit. Those investments with original maturities of greater than three months and remaining maturities of less than 12 months are considered short-term investments. Those investments with maturities greater than 12 months are considered long-term investments. The Company’s investments classified as available-for-sale are recorded at fair value based upon quoted market prices at period end. Unrealized gains and losses for available-for-sale debt investments that are deemed temporary in nature are recorded in accumulated other comprehensive income (loss) as a separate component of stockholder’ equity. Marketable equity securities are equity securities with readily determinable fair value, and are measured and recorded at fair value. Realized and unrealized gains or losses resulting from changes in value and sale of the Company’s marketable equity investments are recorded in other income (expenses) in the consolidated statement of operations.

A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the security. Premiums and discounts are amortized (accreted) over the life of the related security as an adjustment to its yield. Dividend and interest income are recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of investments sold.

Fair Value of Financial Instruments

Carrying amounts of certain of the Company’s financial instruments including cash equivalents, investments, receivables, accounts payable and accrued liabilities approximate fair value (refer to Note 4).

Property and Equipment

Property and equipment (except for costs of construction of certain long-lived assets — refer to Note 8) are recorded at cost and depreciated over their estimated useful lives using the straight-line method. Computer equipment, laboratory equipment, and furniture and fixtures are depreciated over three to five years. Leasehold improvements are recorded at cost and amortized over the term of the lease or their useful life, whichever is shorter.

Impairment of Long-Lived Assets

The Company continually evaluates whether events or circumstances have occurred that indicate that the estimated remaining useful life of its long-lived assets may warrant revision or that the carrying value of these assets may be impaired. If the Company determines that an impairment trigger has been met, the Company evaluates the realizability of its long-lived assets based on a comparison of projected undiscounted cash flows from use and eventual disposition with the carrying value of the related asset. Any write-downs (which are measured based on the difference between the fair value and the carrying value of the asset) are treated as permanent reductions in the carrying amount of the assets (asset group). Based on this evaluation, the Company believes that, as of each of the balance sheet dates presented, none of the Company’s long-lived assets were impaired.

Revenue Recognition

Substantially all of the Company’s revenues to date have been generated from its collaboration agreements.

The Company’s collaboration agreements include multiple performance obligations comprised of promised services, or bundles of services, that are distinct. Services that are not distinct are combined with other services in the agreement until they form a distinct bundle of services. The Company’s process for identifying performance obligations and an enumeration of each obligation for each agreement is outlined in Note 3 “Collaboration Agreements.” Determining the performance obligations within a collaboration agreement often involves significant judgment and is specific to the facts and circumstances contained in each agreement.

The Company has identified the following material promises under its collaboration agreements: (1) license of FibroGen technology, (2) the performance of co-development services, including manufacturing of clinical supplies and other services during the development period, and (3) manufacture of commercial supply. The evaluation as to whether these promises are distinct, and therefore represent separate performance obligations, is described in more details in Note 3 “Collaboration Agreements.”

For revenue recognition purposes, the Company determines that the term of its collaboration agreements begin on the effective date and ends upon the completion of all performance obligations contained in the agreements. In each agreement, the contract term is defined as the period in which parties to the contract have present and enforceable rights and obligations. The Company believes that the existence of what it considers to be substantive termination penalties on the part of the counterparty create sufficient incentive for the counterparty to avoid exercising its right to terminate the agreement unless in exceptionally rare situations.

The transaction price for each collaboration agreement is determined based on the amount of consideration the Company expects to be entitled for satisfying all performance obligations within the agreement. The Company’s collaboration agreements include payments to the Company of one or more of the following: non-refundable upfront license fees; co-development billings; development, regulatory, and commercial milestone payments; payments from sales of active pharmaceutical ingredient (“API”); and royalties on net sales of licensed products.

Upfront license fees are non-contingent and non-refundable in nature and are included in the transaction price at the point when the license fees become due to the Company. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less.

Co-development billings resulting from the Company’s research and development efforts, which are reimbursable under its collaboration agreements, are considered variable consideration. Determining the reimbursable amount of research and development efforts requires detailed analysis of the terms of the collaboration agreements and the nature of the research and development efforts incurred. Determining the amount of variable consideration from co-development billings requires the Company to make estimates of future research and development efforts, which involves significant judgment. Co-development billings are allocated entirely to the co-development services performance obligation when amounts are related specifically to research and development efforts necessary to satisfy the performance obligation, and such an allocation is consistent with the allocation objective.

Milestone payments are also considered variable consideration, which requires the Company to make estimates of when achievement of a particular milestone becomes probable. Similar to other forms of variable consideration, milestone payments are included in the transaction price when it becomes probable that such inclusion would not result in a significant revenue reversal. Milestone payments are therefore included in the transaction price when achievement of the milestone becomes probable.

Product revenue consists of sales of commercial-grade API used in support of pre-commercial validation work. In 2018, the Company recorded revenue from commercial-grade API sales to Astellas based on a transaction price that is subject to potential future adjustments. This represents a form of variable consideration. With respect to these sales in 2018, the transaction price will be adjusted at the time the roxadustat listed price is issued by the Japanese Ministry of Health, Labour and Welfare to reflect differences between estimated and actual listed price, yield from the manufacture of bulk product tablets, and bulk product manufacturing costs. The Company evaluates the latest available facts and circumstances, including listed prices of comparable drug products in Japan and historical bulk drug product manufacturing yields and costs, to determine whether any adjustments to the estimated transaction price is necessary. As of December 31, 2018, no new facts or circumstances were available to warrant an adjustment to the transaction price.

For arrangements that include sales-based royalties and for which the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from its collaboration arrangements.

The transaction price is allocated to performance obligations based on their relative standalone selling price (“SSP”), with the exception of co-development billings allocated entirely to co-development services performance obligations. The SSP is determined based on observable prices at which the Company separately sells the products and services. If an SSP is not directly observable, then the Company will estimate the SSP considering marketing conditions, entity-specific factors, and information about the customer or class of customer that is reasonably available. The process for determining SSP involves significant judgment and includes consideration of multiple factors, including assumptions related to the market opportunity and the time needed to commercialize a product candidate pursuant to the relevant license, estimated direct expenses and other costs, which include the rates normally charged by contract research and contract manufacturing organizations for development and manufacturing obligations, and rates that would be charged by qualified outsiders for committee services.

Significant judgment may be required in determining whether a performance obligation is distinct, determining the amount of variable consideration to be included in the transaction price, and estimating the SSP of each performance obligation. An enumeration of the Company’s significant judgments is outlined in Note 3 “Collaboration Agreements.”

For each performance obligation identified within an arrangement, the Company determines the period over which the promised services are transferred and the performance obligation is satisfied. Service revenue is recognized over time based on progress toward complete satisfaction of the performance obligation. The Company uses an input method to measure progress toward the satisfaction of co-development services and certain other related performance obligations, which is based on costs of labor hours or full time equivalents and out-of-pocket expenses incurred relative to total expected costs to be incurred. The Company believes this measure of progress provides a faithful depiction of the transfer of services because other measures do not measure as accurately how the Company transfers its performance obligations to its collaboration partners.

Research and Development Expenses

Research and development expenses consist of independent research and development costs and the gross amount of costs associated with work performed under collaboration agreements. Research and development costs include employee-related expenses, expenses incurred under agreements with clinical research organizations (“CROs”), other clinical and preclinical costs and allocated direct and indirect overhead costs, such as facilities costs, information technology costs and other overhead. All research and development costs are expensed as incurred.

Clinical Trial Accruals

Clinical trial costs are a component of research and development expenses. The Company accrues and expenses clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research organizations and clinical sites. The Company determines the costs to be recorded based upon validation with the external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services.

General and Administrative Expenses

General and administrative expenses consist primarily of employee-related expenses for executive, operational, finance, legal, compliance and human resource functions. Other general and administrative expenses include facility-related costs and professional fees, accounting and legal services, other outside services, recruiting fees and expenses associated with obtaining and maintaining patents.

Income Taxes

The Company utilizes the asset and liability method of accounting for income taxes which requires the recognition of deferred tax assets and liabilities for expected future consequences of temporary differences between the financial reporting and income tax bases of assets and liabilities using enacted tax rates. Management makes estimates, assumptions and judgments to determine the Company’s provision for income taxes and also for deferred tax assets and liabilities, and any valuation allowances recorded against the Company’s deferred tax assets. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent the Company believes that recovery is not likely, the Company must establish a valuation allowance.

The calculation of the Company’s current provision for income taxes involves the use of estimates, assumptions and judgments while taking into account current tax laws, interpretation of current tax laws and possible outcomes of future tax audits. The Company has established reserves to address potential exposures related to tax positions that could be challenged by tax authorities. Although the Company believes its estimates, assumptions and judgments to be reasonable, any changes in tax law or its interpretation of tax laws and the resolutions of potential tax audits could significantly impact the amounts provided for income taxes in the Company’s consolidated financial statements.

The calculation of the Company’s deferred tax asset balance involves the use of estimates, assumptions and judgments while taking into account estimates of the amounts and type of future taxable income. Actual future operating results and the underlying amount and type of income could differ materially from the Company’s estimates, assumptions and judgments thereby impacting the Company’s financial position and results of operations.

The Company has adopted ASC 740-10, Accounting for Uncertainty in Income Taxes, that prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of uncertain tax positions taken or expected to be taken in the Company’s income tax return, and also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure and transition.

The Company includes interest and penalties related to unrecognized tax benefits within income tax expense in the Consolidated Statements of Operations.

Stock-Based Compensation

The Company maintains equity incentive plans under which incentive and nonqualified stock options are granted to employees and non-employee consultants. Compensation expense relating to non-employee stock options has not been material for all the periods presented.

The Company measures and recognizes compensation expense for all stock options and restricted stock units (“RSUs”) granted to its employees and directors based on the estimated fair value of the award on the grant date. The Company uses the Black-Scholes valuation model to estimate the fair value of stock option awards. The fair value is recognized as expense, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award, on a straight-line basis. The Company believes that the fair value of stock options granted to non-employees is more reliably measured than the fair value of the services received. As such, the fair value of the unvested portion of the options granted to non-employees is re-measured each period. The resulting increase in value, if any, is recognized as expense during the period the related services are rendered on a straight-line basis. The determination of the grant date fair value of options using an option pricing model is affected by the Company’s estimated Common Stock fair value and requires management to make a number of assumptions including the expected life of the option, the volatility of the underlying stock, the risk-free interest rate and expected dividends.

Comprehensive Income (Loss)

The Company is required to report all components of comprehensive income (loss), including net loss, in the consolidated financial statements in the period in which they are recognized. Comprehensive income (loss) is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources, including unrealized gains and losses on investments and foreign currency translation adjustments. Comprehensive gains (losses) have been reflected in the consolidated statements of comprehensive income (loss) for all periods presented.

Recently Issued and Adopted Accounting Guidance

New Revenue Standards

In May 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2014-09, Revenue from Contracts with Customers (Topic 606) (“ASU 2014-09”), which supersedes the revenue recognition requirements in Accounting Standards Codification (“ASC”) 605, Revenue Recognition. ASU 2014-09 is based on the principle that revenue is recognized to depict the transfer of goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. Subsequently, the FASB has issued the following standards related to ASU 2014-09: ASU No. 2016-08, Revenue from Contracts with Customers (Topic 606): Principal versus Agent Considerations; ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606): Identifying Performance Obligations and Licensing; ASU No. 2016-12, Revenue from Contracts with Customers (Topic 606): Narrow-Scope Improvements and Practical Expedients; and ASU No. 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers (collectively, the “new revenue standards”).

Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied.

The Company adopted the new revenue standards as of January 1, 2018 using the full retrospective method, which required the Company to recast the prior reporting periods presented in the consolidated financial statements. The primary impact upon adoption of the new revenue standards relates to the manner in which revenue is recognized for co-development billings and milestone payments under the Company’s collaboration arrangements. Under the new revenue standards, both of these elements of consideration are considered variable consideration which requires the Company to make estimates of when co-development billings become due or when achievement of a particular milestone becomes probable. Payments are included in the transaction price when it becomes probable that inclusion would not lead to a significant revenue reversal.

The Company has recast its consolidated statement of operations and balance sheet from amounts previously reported due to the adoption of the new revenue standards. The adoption of the new revenue standards had no impact to the Company’s previously reported consolidated statement of cash flows.

Select line items from the Company’s consolidated statement of operations and balance sheet, which reflect the adoption of the new revenue standards are as follows (in thousands):

	Year Ended December 31, 2017									Year Ended December 31, 2016
	As Previously Reported			New Revenue Standards Adjustment			As Recast			As Previously Reported			New Revenue Standards Adjustment			As Recast
Statement of Operations
License revenue	$	96,056		$	(86,123	)	$	9,933		$	137,352		$	(86,745	)	$	50,607
Development and other revenue		29,612			91,451			121,063			42,225			90,357			132,582
Total revenue		125,668			5,328			130,996			179,577			3,612			183,189
Net loss		(126,203	)		5,328			(120,875	)		(61,680	)		3,612			(58,068	)
Net loss per share - basic and diluted	$	(1.73	)	$	0.07		$	(1.66	)	$	(0.98	)	$	0.05		$	(0.93	)

										December 31, 2017
										As Previously Reported			New Revenue Standards Adjustment			As Recast
Balance Sheet
Deferred revenue, current										$	7,968		$	8,702		$	16,670
Deferred revenue, net of current											112,231			26,010			138,241
Accumulated deficit											(595,945	)		(34,712	)		(630,657	)

The adoption of the new revenue standards also resulted in the following changes in the accumulated deficit as of December 31, 2016 and 2015:

	As Previously Reported			New Revenue Standards Adjustment			As Recast
Accumulated Deficit
As of December 31, 2016	$	(469,742	)	$	(40,040	)	$	(509,782	)
As of December 31, 2015	$	(408,062	)	$	(43,652	)	$	(451,714	)

ASU 2016-01

In January 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall (Subtopic 825-10). This guidance requires equity investments that are not accounted for under the equity method of accounting to be measured at fair value with changes recognized in net income, simplifies the impairment assessment of certain equity investments, and updates certain presentation and disclosure requirements. This guidance was effective for the annual reporting period beginning after December 15, 2017 and interim periods within those annual periods. The Company adopted this guidance as of January 1, 2018 using the modified retrospective approach. The impacts to the Company’s accumulated other comprehensive loss and accumulated deficit upon adoption of this guidance are as follows (in thousands):

	Accumulated Other Comprehensive Loss			Accumulated Deficit
Balance at December 31, 2017	$	(1,795	)	$	(630,657	)	*
Impact of change in accounting principle upon adoption of ASU 2016-01		(1,250	)		1,250
Opening balance as of January 1, 2018	$	(3,045	)	$	(629,407	)

*	Recast to reflect the adoption of the new revenue standards. See above.

The adoption of this guidance had no impact to the Company’s consolidated statement of cash flows for the year ended December 31, 2018.

ASU 2017-09

In May 2017, the FASB issued ASU 2017-09, Compensation - Stock Compensation (Topic 718): Scope of Modification Accounting. This guidance provides guidance about which changes to the terms or conditions of a stock-based payment award require an entity to apply modification accounting in Topic 718. This guidance was effective for annual reporting period beginning after December 15, 2017, including interim periods. The Company adopted this guidance as of January 1, 2018, and the adoption of this guidance had no impact to the Company’s consolidated financial statements.

ASU 2016-16

In October 2016, the FASB issued ASU 2016-16, Intra-Entity Transfers of Assets Other Than Inventory. This guidance requires companies to recognize the income tax effects of intercompany sales or transfer of assets, other than inventory, in the income statement as income tax expense (or benefit) in the period the sale or transfer occurs. The exception to recognizing the income tax effects of intercompany sales or transfer sales or transfer of assets remains in place for intercompany inventory sales and transfers. This guidance was effective for annual reporting period beginning after December 15, 2017, including interim periods. The Company adopted this guidance as of January 1, 2018 using the modified retrospective method. The adoption of this guidance did not result in any recognition of previously unrecognized deferred charges using a modified retrospective method, thus had no impact to the Company’s consolidated financial statements.

Recently Issued Accounting Guidance Not Yet Adopted

In August 2018, the FASB issued ASU 2018-15, Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract. This guidance requires capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal-use software license). This guidance should be applied either retrospectively or prospectively, and is effective for annual reporting period beginning after December 15, 2019 including interim periods, with early adoption permitted. The Company is currently evaluating the impact on its consolidated financial statements upon the adoption of this guidance.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework—Changes to the Disclosure Requirements for Fair Value Measurement. This guidance amends existing fair value measurement disclosure requirements by adding, changing, or removing certain disclosures. This guidance is effective for annual reporting period beginning after December 15, 2019 including interim periods, with early adoption permitted. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. The Company does not anticipate a material impact to its consolidated financial statements upon adoption of this guidance.

In June 2018, the FASB issued ASU 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. This guidance expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from nonemployees. The guidance also specifies that Topic 718 applies to all share-based payment transactions in which a grantor acquires goods or services to be used or consumed in a grantor’s own operations by issuing share-based payment awards. This guidance is effective for annual reporting period beginning after December 15, 2018, including interim periods. The Company will adopt this guidance on January 1, 2019 and does not anticipate a material impact to its consolidated financial statements upon adoption.

In February 2018, the FASB issued ASU 2018-02, Income Statement - Reporting Comprehensive Income: Reclassification of Certain Tax effects from Accumulated Other Comprehensive Income. This guidance allows for the reclassification from accumulated other comprehensive income to retained earnings for the stranded tax effects arising from the change in the reduction of the United States (“U.S.”) federal statutory income tax rate from 35% to 21%. This guidance is effective for annual reporting period beginning after December 15, 2018, including interim periods, with early adoption permitted. The Company will adopt this guidance on January 1, 2019 and anticipate a reclassification of $0.6 million from its accumulated other comprehensive loss to its accumulated deficit upon adoption.

In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU 2016-13”). This guidance requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. The measurement of expected credit losses is based on historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability. In November 2018, the FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments-Credit Losses (“ASU 2018-19”), which clarifies certain topics included within ASU 2016-13. ASU 2016-13 and ASU 2018-19 are effective for the annual reporting period beginning after December 15, 2019, including interim periods within that reporting period. The Company is currently evaluating the impact on its consolidated financial statements upon the adoption of this guidance.

In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) (“ASU 2016-02”). Under this guidance, an entity is required to recognize right-of-use assets and lease liabilities on its balance sheet and disclose key information about leasing arrangements. This guidance offers specific accounting guidance for a lessee, a lessor and sale and leaseback transactions. Lessees and lessors are required to disclose qualitative and quantitative information about leasing arrangements to enable a user of the financial statements to assess the amount, timing and uncertainty of cash flows arising from leases. In July 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements (“ASU 2018-11”), which provides entities the option to initially apply ASU 2016-02 at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. ASU 2016-02 and ASU 2018-11 are effective for the annual reporting period beginning after December 15, 2018, including interim periods within that reporting period. The Company will adopt this guidance as of January 1, 2019 and utilize the modified retrospective transition method through a cumulative-effect adjustment at the beginning of the first quarter of 2019. Based on the current evaluation, the Company anticipates a recognition of approximately $47 million to $62 million in right-of-use assets and approximately $57 million to $67 million in lease liabilities, respectively, upon adoption of this guidance, for its operating leases and facility leases disclosed in Note 8 to its consolidated balance sheets. Accordingly, the related balances as of December 31, 2018 in property and equipment, net, and long-term portion of lease financing obligations would be removed. The Company does not anticipate a material impact to its consolidated statement of operations or consolidated statement of cash flows upon adoption of this guidance.

Collaboration Agreements

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Collaboration Agreements

3.	Collaboration Agreements

Astellas Agreements

Japan Agreement

In June 2005, the Company entered into a collaboration agreement with Astellas Pharma Inc. (“Astellas”) for the development and commercialization (but not manufacture) of roxadustat for the treatment of anemia in Japan (“Japan Agreement”). Under this agreement, Astellas paid license fees and other consideration totaling $40.1 million (such amounts were fully received as of February 2009). The Japan Agreement also provides for additional development and regulatory approval milestone payments up to $117.5 million, a commercial sales related milestone of $15.0 million and additional consideration based on net sales (as defined) in the low 20% range after commercial launch.

During the second quarter of 2018, Astellas reported positive results from the final phase 3 CKD-dialysis trial of roxadustat in Japan, indicating that Astellas was ready to make an NDA submission for the treatment of anemia with roxadustat in CKD-dialysis patients in 2018. The Company evaluated the regulatory milestone payment associated with NDA submission in Japan based on variable consideration requirements under the current revenue standards and concluded that this milestone became probable of being achieved in the second quarter of 2018. Accordingly, the consideration of $15.0 million associated with this milestone was included in the transaction price and allocated to performance obligations under the Japan Agreement in the second quarter of 2018, substantially all of which was recognized as revenue during the year ended December 31, 2018 from performance obligations satisfied or partially satisfied.

On November 30, 2018, FibroGen and Astellas entered into an amendment to the Japan Agreement that will allow Astellas to manufacture roxadustat drug product for commercialization in Japan (the “Japan Amendment”). Under this amendment, FibroGen would continue to manufacture and deliver to Astellas roxadustat API. The commercial terms of the Japan Agreement relating to the transfer price for roxadustat for commercial use remain substantially the same, reflecting an adjustment for the manufacture of drug product by Astellas rather than FibroGen. This amendment obligates Astellas to purchase API from the Company, of which $20.9 million was delivered to Astellas in the second quarter of 2018 under a material transfer agreement to conduct commercial scale manufacturing validation for roxadustat drug product in anticipation of commercial launch in Japan. The remaining $43.9 million of API was delivered to Astellas in December 2018.

Europe Agreement

In April 2006, the Company entered into a separate collaboration agreement with Astellas for the development and commercialization of roxadustat for the treatment of anemia in Europe, the Middle East, the Commonwealth of Independent States and South Africa (“Europe Agreement”). Under the terms of the Europe Agreement, Astellas paid license fees and other upfront consideration totaling $320.0 million (such amounts were fully received as of February 2009). The Europe Agreement also provides for additional development and regulatory approval milestone payments up to $425.0 million. Under the Europe Agreement, Astellas committed to fund 50% of joint development costs for Europe and North America, and all territory-specific costs. The Europe Agreement also provides for tiered payments based on net sales of product (as defined) in the low 20% range.

In the fourth quarter of 2018, the Company’s was engaged in the final stages of review with its partners over the proposed development of roxadustat for the treatment of chemotherapy induced anemia (“CIA”). AstraZeneca and Astellas approved the program in December 2018 and January 2019, respectively. Costs associated with the development of this indication are expected to be shared 50-50 between the Company’s two partners. For revenue recognition purposes, the Company concluded that this new indication represents a modification to the Europe agreements and will be accounted for separately, meaning the development costs associated with the new indications are distinct from the original development costs. The development service period for roxadustat for the treatment of CIA under the Europe Agreement is estimated to continue through the end of 2023 to allow for development of this indication.

AstraZeneca Agreements

U.S./Rest of World Agreement

Effective July 30, 2013, the Company entered into a collaboration agreement with AstraZeneca for the development and commercialization of roxadustat for the treatment of anemia in the U.S. and all other countries in the world, other than China, not previously licensed under the Astellas Europe and Astellas Japan Agreements (“U.S./RoW Agreement”). It also excludes China, which is covered by a separate agreement with AstraZeneca described below. Under the terms of the U.S./RoW Agreement, AstraZeneca has agreed to pay upfront, non-contingent and time-based payments totaling $374.0 million, which were fully received in various amounts through June 2016. In addition, the U.S./RoW Agreement also provides for development and regulatory approval based milestone payments of up to $550.0 million, which include potential future indications which the companies choose to pursue, and commercial related milestone payments of up to $325.0 million.

Under the U.S./RoW Agreement, the Company and AstraZeneca will share equally in the development costs of roxadustat not already paid for by Astellas, up to a total of $233.0 million (i.e. the Company’s share of development costs is $116.5 million, which was reached in 2015). Development costs incurred by FibroGen during the development period in excess of the $233.0 million (aggregated spend) are fully reimbursed by AstraZeneca. AstraZeneca will pay the Company tiered royalty payments on AstraZeneca’s future net sales (as defined in the agreement) of roxadustat in the low 20% range. In addition, the Company will receive a transfer price for delivery of commercial product based on a percentage of AstraZeneca’s net sales (as defined in the agreement) in the low- to mid-single digit range.

China Agreement

Effective July 30, 2013, the Company (through its subsidiaries affiliated with China) entered into a collaboration agreement with AstraZeneca for the development and commercialization (but not manufacture) of roxadustat for the treatment of anemia in China (“China Agreement”). Under the terms of the China Agreement, AstraZeneca agreed to pay upfront consideration totaling $28.2 million, which were fully received in 2014. In addition, the China Agreement provides for AstraZeneca to pay regulatory approval and other approval related milestones of up to $161.0 million. The China Agreement also provides for sales related milestone payments of up to $167.5 million and contingent payments of $20.0 million related to possible future compounds. The China Agreement is structured as a 50/50 profit or loss share (as defined) and provides for joint development costs (including capital and equipment costs for construction of the manufacturing plant in China), to be shared equally during the development.

In September 2016, AstraZeneca approved the protocol related to the development of roxadustat for the treatment of anemia in patients with myelodysplastic syndrome (“MDS”), for which the Company has received approval from then the China Food and Drug Administration (“CFDA,” now known as the National Medicine Products Administration (“NMPA”)) for its clinical trial application for a Phase 2/3 trial and acceptance of its Investigational New Drug Application from the U.S. Food and Drug Administration for a Phase 3 trial. As a result, for revenue recognition purposes, during the third quarter of 2016, the Company extended the estimated joint development service period for the AstraZeneca agreements from the end of 2018 to the end of 2020, to allow for development of MDS.

As mentioned above, in the fourth quarter of 2018, the Company was engaged in the final stages of review with its partners over the proposed development of roxadustat for the treatment of CIA. AstraZeneca and Astellas approved the program in December 2018 and January 2019, respectively. Costs associated with the development of this indication are expected to be shared 50-50 between the Company’s two partners. In addition to CIA, in December 2018, anemia of chronic inflammation (“ACI”) and multiple myeloma (“MM”) have been approved for development by AstraZeneca and is expected to be fully funded by them. For revenue recognition purposes, the Company concluded that the addition of these new indications represents a modification to the collaboration agreements and will be accounted for separately, meaning the development costs associated with the new indications are distinct from the original development costs. The development service period for roxadustat for the treatment of CIA, ACI and MM under the AstraZeneca agreements is estimated to continue through the end of 2024, to allow for development of these additional indications.

In October 2017, then the CFDA (now known as the NMPA) accepted the Company’s recently submitted New Drug Application (“NDA”) for registration of roxadustat for anemia in dialysis-dependent CKD and non-dialysis-dependent CKD (NDD-CKD) patients. This NDA submission triggered a $15.0 million milestone payment to the Company by AstraZeneca, which became probable of being achieved during the third quarter of 2017, and therefore partially recognized as revenue under the new revenue standards during 2017.

On December 17, 2018, FibroGen (China) Medical Technology Development Co., Ltd. (“FibroGen China”), received marketing authorization from the NMPA for roxadustat, a first-in-class hypoxia-inducible factor prolyl hydroxylase inhibitor, for the treatment of anemia caused by CKD in patients on dialysis. This approval triggered a $6.0 million milestone payable to the Company by AstraZeneca. On December 29, 2018, FibroGen China received First Manufacturing Approval for a Product in the Field in the Territory , which allows production for Phase IV clinical studies, patients’ early experience programs, donation programs, as well as to supply products for testing and assessments required prior to launch. This approval triggered a $6.0 million milestone payable to the Company by AstraZeneca. Approximately $9.9 million of the total $12.0 million milestone payables was recognized as revenue during the fourth quarter of 2018 from performance obligations satisfied or partially satisfied.

Accounting for the Astellas Agreements

For each of the Astellas agreements, the Company has evaluated the promised services within the respective arrangements and has identified performance obligations representing those services and bundles of services that are distinct.

Promised services that were not distinct have been combined with other promised services to form a distinct bundle of promised services, with revenue being recognized on the bundle of services rather than the individual services. There are no right-of-return provisions for the delivered items in the Astellas agreements.

As of December 31, 2018, the transaction price for the Japan Agreement included $40.1 million of non-contingent upfront payments, $37.5 million of variable consideration related to payments for milestones considered probable of being achieved, and $12.1 million of variable consideration related to co-development billings. The transaction price for the Europe Agreement included $320.0 million of non-contingent upfront payments, $90.0 million of variable consideration related to payments for milestones considered probable of being achieved, and $180.9 million of variable consideration related to co-development billings.

For revenue recognition purposes, the Company determined that the term of each collaboration agreement with Astellas begins on the effective date and ends upon the completion of all performance obligations contained in the agreement. The contract term is defined as the period in which parties to the contract have present and enforceable rights and obligations. The Company believes that the requirement to continue funding development for a substantive period of time and loss of product rights, along with non-refundable upfront payments already remitted by Astellas, create significant disincentive for Astellas to exercise its right to terminate the agreements.

For the Astellas agreements, the Company allocated the transaction price to the various performance obligations based on the relative SSP of each performance obligation, with the exception of co-development billings allocated entirely to co-development services performance obligations.

For the technology license under the Japan Agreement and Europe Agreement, SSP was determined primarily by using the discounted cash flow (“DCF”) method, which aggregates the present value of future cash flows to determine the valuation as of the effective date of each of the agreements. The DCF method involves the following key steps: 1) the determination of cash flow forecasts and 2) the selection of a range of comparative risk-adjusted discount rates to apply against the cash flow forecasts. The discount rates selected were based on expectations of the total rate of return, the rate at which capital would be attracted to the Company and the level of risk inherent within the Company. The discounts applied in the DCF analysis ranged from 17.5% to 20.0%. The Company’s cash flow forecasts were derived from probability-adjusted revenue and expense projections by territory. Such projections included consideration of taxes and cash flow adjustments. The probability adjustments were made after considering the likelihood of technical success at various stages of clinical trials and regulatory approval phases. SSP also considered certain future royalty payments associated with commercial performance of the Company’s compounds, transfer prices and expected gross margins.

The promised services that were analyzed, along with their general timing of satisfaction and recognition as revenue, are as follows:

(1)

License to the Company’s technology existing at the effective date of the agreements. For both of the Astellas agreements, the license was delivered at the beginning of the agreement term. In both cases, the Company concluded at the time of the agreement that its collaboration partner, Astellas, would have the knowledge and capabilities to fully exploit the licenses without the Company’s further involvement. However, the Japan Agreement has contractual limitations that might affect Astellas’ ability to fully exploit the license and therefore, potentially, the conclusion as to whether the license is capable of being distinct. In the Japan Agreement, Astellas does not have the right to manufacture commercial supplies of the drug. In order to determine whether this characteristic of the agreement should lead to a conclusion that the license was not distinct in the context of the agreement, the Company considered the ability of Astellas to benefit from the license together with other resources readily available to Astellas. Finally, the Company considered the fact that at the time of delivery of the license, the development services were beyond the preclinical development phase and any remaining development work in either agreement would not be expected to result in any significant modification or customization to the licensed technology. As such, the development services are separately identifiable from the licensed technology, indicating that the license is a distinct performance obligation.

Manufacturing rights. In the case of the Japan Agreement, the Company retained manufacturing rights largely because of the way the parties chose for FibroGen to be compensated under the agreement. At the time the agreement was signed, the Company believed that it was more advantageous upon commercialization to have a transfer price revenue model in place as opposed to a traditional sales-based model. The manufacturing process does not require specialized knowledge or expertise uniquely held by FibroGen, and notwithstanding contractual restrictions, Astellas could employ manufacturing services from readily available third parties in order to benefit from the license. Therefore, along with the foregoing paragraph, the Company determined that the license in Japan is a distinct performance obligation despite the retention of manufacturing rights by the Company.

In summary, the Company concludes that item (1) represents a performance obligation. The portion of the transaction price allocated to this performance obligation based on a relative SSP basis is recognized as revenue in its entirety at the point in time the license transfers to Astellas.

(2)

Co-development services (Europe Agreement). This promise relates to co-development services that were reasonably expected to be performed by the Company at the time the collaboration agreement was signed and is considered distinct. Co-development billings are allocated entirely to the co-development services performance obligation as amounts are related specifically to research and development efforts necessary to satisfy the performance obligation, and such an allocation is consistent with the allocation objective. Revenue is recognized over time based on progress toward complete satisfaction of the performance obligation. The Company uses an input method to measure progress toward the satisfaction of the performance obligation, which is based on costs of labor hours and out-of-pocket expenses incurred relative to total expected costs to be incurred. The measure of progress is updated each reporting period. Co-development services are expected to continue over the development period that is currently estimated to continue through the end of 2019. In addition, the Company concluded that the new indication related to CIA approved in January 2019 represents a modification to the Europe agreements at that time and will be accounted for separately, for which the development service period is estimated to continue through the end of 2023. There was no provision for co-development services in the Japan Agreement.

(3)	License to the Company’s technology developed during the term of the agreement and development (referred to as “when and if available”) and information sharing services. These promises are generally satisfied throughout the term of the agreements.

(4)	Manufacturing of clinical supplies of products. This promise is satisfied as supplies for clinical product are delivered for use in the Company’s clinical trial programs during the development period, or pre-commercialization period.

(5)	Committee service. This promise is satisfied throughout the course of the agreements as meetings are attended.

Items (3)-(5) are bundled into a single performance obligation which is distinct given the fact that all are highly interrelated during the development period (pre-commercial phase of development) such that satisfying them independently is not practicable. Revenue is recognized over time based on progress toward complete satisfaction of the performance obligation. The Company uses an input method to measure progress toward the satisfaction of the performance obligation, which is based on costs of labor hours or full time equivalents and out-of-pocket expenses incurred relative to total expected costs to be incurred. The measure of progress is updated each reporting period.

(6)

Manufacturing commercial supplies of products. This promised service is distinct as services are not interrelated with any of the other performance obligations. Payments received for commercial supplies of products represent sales-based payments related predominately to the license of intellectual property under both Astellas agreements. Revenue is recognized as supplies are shipped for commercial use during the commercialization period. To date, no such revenue has been recognized.

In 2018, the Company recorded revenue from commercial-grade API sales to Astellas to conduct commercial scale manufacturing validation based on a transaction price that is subject to potential future adjustments. This represents a form of variable consideration. The Company evaluates the latest available facts and circumstances to determine whether any adjustments to the estimated transaction price is necessary. As of December 31, 2018, no new facts or circumstances were available to warrant an adjustment to the transaction price.

Accounting for the AstraZeneca Agreements

The Company evaluated whether the U.S./RoW Agreement and China Agreement should be accounted for as a single or separate arrangements and concluded that the agreements should be accounted for as a single arrangement with the presumption that two or more agreements executed with a single customer at or around the same time should be presumed to be a single arrangement. The key points the Company considered in reaching this conclusion are as follows:

1.	While the two agreements were largely negotiated separately, those negotiations proceeded concurrently, and were intended to be completed contemporaneously, presuming AstraZeneca decided to proceed with licenses in all regions available.

Throughout negotiations for both agreements, the Company and the counterparties understood and considered the possibility that one arrangement may be executed without the execution of the other arrangement. However, the preference for the Company and the counterparties during the negotiations was to execute both arrangements concurrently.

The two agreements were executed as separate agreements because different development, regulatory and commercial approaches required certain terms of the agreements to be structured differently, rather than because the Company or the counterparties considered the agreements to be fundamentally separate negotiations.

Accordingly, as the agreements are being accounted for as a single arrangement, upfront and other non-contingent consideration received and to be received has been and will be pooled together and allocated to each of the performance obligations in both the U.S./RoW Agreement and China Agreement based on their relative SSPs.

For each of the AstraZeneca agreements, the Company has evaluated the promised services within the respective arrangements and has identified performance obligations representing those services and bundled services that are distinct.

Promised services that were not distinct have been combined with other promised services to form a distinct bundle of promised services, with revenue being recognized on the bundle of services rather than the individual promised services. There are no right-of-return provisions for the delivered items in the AstraZeneca agreements.

As of December 31, 2018, the transaction price for the U.S./RoW Agreement and China Agreement included $402.2 million of non-contingent upfront payments, $42.0 million of variable consideration related to payments for milestones considered probable of being achieved, and $621.6 million of variable consideration related to co-development billings.

For the AstraZeneca agreements, the Company allocated the transaction price to the various performance obligations based on the relative SSP of each performance obligation, with the exception of co-development billings. Co-development billings under the U.S./RoW Agreement were allocated entirely to the U.S./RoW co-development services performance obligation, and co-development billings under the China Agreement were allocated entirely to the combined performance obligation under the China Agreement.

For revenue recognition purposes, the Company determined that the term of its collaboration agreements with AstraZeneca begin on the effective date and ends upon the completion of all performance obligations contained in the agreements. The contract term is defined as the period in which parties to the contract have present and enforceable rights and obligations. The Company believes that the requirement to continue funding development for a substantive period of time and the loss of product rights, along with non-refundable upfront payments already remitted by AstraZeneca, represent substantive termination penalties that create significant disincentive for AstraZeneca to exercise its right to terminate the agreement.

For the technology license under the AstraZeneca U.S./RoW Agreement, SSP was determined based on a two-step process. The first step involved determining an implied royalty rate that would result in the net present value of future cash flows to equal to zero (i.e. where the implied royalty rate on the transaction would equal the target return for the investment). This results in an upper bound estimation of the magnitude of royalties that a hypothetical acquirer would reasonably pay for the forecasted cash flow stream. The Company’s cash flow forecasts were derived from probability-adjusted revenue and expense projections. Such projections included consideration of taxes and cash flow adjustments. The probability adjustments were made after considering the likelihood of technical success at various stages of clinical trials and regulatory approval phases. The second step involved applying the implied royalty rate, which was determined to be 40%, against the probability-adjusted projected net revenues by territory and determining the value of the license as the net present value of future cash flows after adjusting for taxes. The discount rate utilized was 17.5%.

U.S./RoW Agreement:

The promised services that were analyzed, along with their general timing of satisfaction and recognition as revenue, are as follows:

(1)

License to the Company’s technology existing at the effective date of the agreements. For the U.S./RoW Agreement, the license was delivered at the beginning of the agreement term. The Company concluded that AstraZeneca has the knowledge and capabilities to fully exploit the license under the U.S./RoW Agreement without the Company’s further involvement. Finally, the Company considered the fact that at the time of delivery of the license, the development services were beyond the preclinical development phase and any remaining development work would not be expected to result in any significant modification or customization to the licensed technology. As such, the development services are separately identifiable from the licensed technology, indicating that the license is a distinct performance obligation. Therefore, the Company has concluded that the license is distinct and represents a performance obligation. The portion of the transaction price allocated to this performance obligation based on a relative SSP basis is recognized as revenue in its entirety at the point in time the license transfers to AstraZeneca.

(2)

Co-development services. This promise relates to co-development services that were reasonably expected to be performed by the Company at the time the collaboration agreement was signed and is distinct. Co-development billings are allocated entirely to the co-development services performance obligation as amounts are related specifically to research and development efforts necessary to satisfy the performance obligation, and such an allocation is consistent with the allocation objective. Revenue is recognized over time based on progress toward complete satisfaction of the performance obligation. The Company uses an input method to measure progress toward the satisfaction of the performance obligation, which is based on costs of labor hours or full time equivalents and out-of-pocket expenses incurred relative to total expected costs to be incurred. Co-development services are expected to continue over the development period that is currently estimated to continue through the end of 2020. In addition, the Company concluded that the addition of the new indications related to CIA, ACI and MM approved during the fourth quarter of 2018 represents a modification to the collaboration agreements and will be accounted for separately, for which the joint development service period is estimated to continue through the end of 2024.

(3)	Manufacturing of clinical supplies of products. This promise is satisfied as supplies for clinical product are delivered for use in the Company’s clinical trial programs during the development period, or pre-commercialization period.

(4)	Information sharing and committee service. These promises are satisfied throughout the course of the agreement as services are provided.

Items (3)-(4) are bundled into a single performance obligation which is distinct given the fact that all are highly interrelated during the development period (pre-commercial phase of development) such that delivering them independently is not practicable. Revenue is recognized over time based on progress toward complete satisfaction of the performance obligation. The Company uses an input method to measure progress toward the satisfaction of the performance obligation, which is based on costs of labor hours or full time equivalents and out-of-pocket expenses incurred relative to total expected costs to be incurred. The measure of progress is updated each reporting period.

(5)

Manufacturing commercial supplies of products. This promise is distinct as services are not interrelated with any of the other performance obligations. Payments received for commercial supplies of products represent sales-based royalties related predominately to the license of intellectual property under the agreement. Revenue is recognized as supplies are shipped for commercial use during the commercialization period. To date, no such revenue has been recognized.

China Agreement:

The performance obligation that were analyzed, along with their general timing of satisfaction and recognition as revenue, are as follows:

•

License to the Company’s technology existing at the effective date of the agreement. The license was delivered at the beginning of the agreement term. However, the China Agreement with AstraZeneca has contractual limitations that might affect AstraZeneca’s ability to fully exploit the license and therefore, potentially, the conclusion as to whether the license is distinct in the context of the agreement. In the China Agreement, AstraZeneca does not have the right to manufacture commercial supplies of the drug. In order to determine whether this characteristic of the arrangement should lead to a conclusion that the license was not distinct in the context of the agreement, the Company considered the ability of AstraZeneca to benefit from the license on its own or together with other resources readily available to AstraZeneca.

For the China Agreement, the Company retained manufacturing rights as an essential part of a strategy to pursue domestic regulatory pathway for product approval which requires the regulatory licensure of the manufacturing facility in order to commence commercial shipment. The prospects for the collaboration as a whole would have been substantially different had manufacturing rights been provided to AstraZeneca. Due to certain regulatory restrictions in China, manufacturing services of commercial drug product in China are not readily available to AstraZeneca or any other parties. Therefore, AstraZeneca cannot benefit from the license on its own or together with other readily available resources. Accordingly, all the promises identified, including co-development services, under the China Agreement have been bundled into a single performance obligation and amounts of the transaction price allocable to this performance obligation are deferred until control of the manufactured commercial drug product has begun to transfer to AstraZeneca. Upon commencement of the transfer of control to commercial drug product, revenue would be recognized in a pattern consistent with estimated deliveries of the commercial drug product.

Summary of revenue recognized under the collaboration agreements

The table below summarizes the accounting treatment for the various performance obligations pursuant to each of the Astellas and AstraZeneca agreements. License amounts identified below are included in the “License revenue” line item in the consolidated statements of operations. All other elements identified below are included in the “Development and other revenue” line item in the consolidated statements of operations.

Amounts recognized as revenue under the Japan Agreement were as follows (in thousands):

		Years Ended December 31,
Agreement	Performance Obligation	2018		2017 *		2016 *
Japan	License revenue	$	14,323	$	—	$	9,548
	Development revenue	$	2,400	$	1,588	$	4,288

*	Recast to reflect the adoption of the new revenue standards. See Note 2.

The transaction price related to consideration received and accounts receivable has been allocated to each of the following performance obligations under the Japan Agreement, along with any associated deferred revenue as follows (in thousands):

Japan Agreement	Cumulative Revenue Through December 31, 2018		Deferred Revenue at December 31, 2018		Total Consideration Through December 31, 2018
License	$	74,089	$	—	$	74,089
Development revenue		13,908		286		14,194
Total license and development revenue	$	87,997	$	286	$	88,283

The revenue recognized under the Japan Agreement for the year ended December 31, 2018 included an increase of $14.9 million resulting from changes to estimated variable consideration in the current year relating to performance obligations satisfied or partially satisfied in previous periods. The remainder of the transaction price related to the Japan Agreement includes $1.4 million of variable consideration from estimated future co-development billing and is expected to be recognized over the remaining development service period.

Amounts recognized as revenue under the Europe Agreement were as follows (in thousands):

		Years Ended December 31,
Agreement	Performance Obligation	2018		2017 *		2016 *
Europe	License revenue	$	—	$	—	$	—
	Development revenue	$	18,503	$	18,523	$	17,487

Recast to reflect the adoption of the new revenue standards. See Note 2.

The transaction price related to consideration received and accounts receivable has been allocated to each of the following performance obligations under the Europe Agreement, along with any associated deferred revenue as follows (in thousands):

Europe Agreement	Cumulative Revenue Through December 31, 2018		Deferred Revenue at December 31, 2018		Total Consideration Through December 31, 2018
License	$	370,481	$	—	$	370,481
Development revenue		202,836		3,225		206,061
Total license and development revenue	$	573,317	$	3,225	$	576,542

The revenue recognized under the Europe Agreement for the year ended December 31, 2018 included an increase in revenue of $0.6 million, resulting from changes to estimated variable consideration in the current year relating to performance obligations satisfied or partially satisfied in previous periods. The remainder of the transaction price related to the Europe Agreement includes $14.3 million of variable consideration from estimated future co-development billing and is expected to be recognized over the remaining development service period.

Amounts recognized as revenue under the U.S./RoW and China Agreements were as follows (in thousands):

		Years Ended December 31,
Agreement	Performance Obligation	2018		2017 *		2016 *
U.S. / RoW and China	License revenue	$	7,946	$	9,933	$	41,059
	Development revenue	$	104,970	$	100,928	$	110,677
	China performance obligation	$	—	$	—	$	—

*	Recast to reflect the adoption of the new revenue standards. See Note 2.

The transaction price related to consideration received and accounts receivable has been allocated to each of the following performance obligations under the U.S./RoW Agreement and China Agreement, along with any associated deferred revenue as follows (in thousands):

U.S. / RoW and China Agreements	Cumulative Revenue Through December 31, 2018		Deferred Revenue at December 31, 2018		Total Consideration Through December 31, 2018
License	$	294,163	$	—	$	294,163
Co-development, information sharing & committee services		408,637		20,521		429,158
China performance obligation		—		125,848		125,848
Total license and development revenue	$	702,800	$	146,369	$	849,169

The revenue recognized under the U.S./RoW Agreement and China Agreement for the year ended December 31, 2018 included an increase in revenue of $20.2 million resulting from changes to estimated variable consideration in the current year relating to performance obligations satisfied or partially satisfied in previous periods. The remainder of the transaction price related to the U.S./RoW Agreement and China Agreement includes $197.4 million of variable consideration from estimated future co-development billing and is expected to be recognized over the remaining development service period, except for amounts allocated to the China performance obligation, which are expected to be recognized in a pattern consistent with estimated deliveries of the commercial drug product.

Product Revenue

As described above, the Japan Amendment obligates Astellas to purchase API from the Company to conduct commercial scale manufacturing validation for roxadustat drug product in anticipation of commercial launch in Japan. The Company fulfilled all the delivery obligations under the term of the Japan Amendment during the year ended December 31, 2018, and recognized the related product revenue of $64.8 million in the same period.

Other Revenues

Other revenues consist primarily of collagen material sold for research purposes. Other revenues were immaterial for each of the three years ended December 31, 2018.

Deferred Revenue

Deferred revenue represents amounts billed to the Company’s collaboration partners for which the related revenues have not been recognized because one or more of the revenue recognition criteria have not been met. The current portion of deferred revenue represents the amount to be recognized within one year from the balance sheet date based on the estimated performance period of the underlying performance obligations. The long term portion of deferred revenue represents amounts to be recognized after one year through the end of the non-contingent performance period of the underlying performance obligations. The long term portion of deferred revenue also includes amounts allocated to the China unit of accounting under the AstraZeneca arrangement as revenue recognition associated with this unit of accounting is tied to the commercial launch of the products within China, which is not expected to occur within the next year.

Fair Value Measurements

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Value Measurements

4.	Fair Value Measurements

In accordance with the authoritative guidance on fair value measurements and disclosures under U.S. GAAP, the Company presents all financial assets and liabilities and any other assets and liabilities that are recognized or disclosed at fair value on a nonrecurring basis. The guidance defines fair value, establishes a framework for measuring fair value in generally accepted accounting principles and expands disclosures about fair-value measurements. The guidance also requires fair value measurements be classified and disclosed in one of the following three categories:

Level 1: Quoted prices in active markets for identical assets or liabilities.

Level 2: Observable inputs other than quoted prices in active markets for identical assets or liabilities.

Level 3: Unobservable inputs.

The Company values certain assets and liabilities, focusing on the inputs used to measure fair value, particularly in instances where the measurement uses significant unobservable (Level 3) inputs. The Company’s financial instruments are valued using quoted prices in active markets (Level 1) or based upon other observable inputs (Level 2). The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and considers factors specific to the asset or liability. In addition, the categories presented do not suggest how prices may be affected by the size of the purchases or sales, particularly with the largest highly liquid financial issuers who are in markets continuously with non-equity instruments, or how any such financial assets may be impacted by other factors such as U.S. government guarantees. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement.

The fair values of the Company’s financial assets that are measured on a recurring basis are as follows (in thousands):

	December 31, 2018
	Level 1		Level 2		Level 3		Total
US treasury notes and bills	$	292,317	$	224,953	$	—	$	517,270
Bond and mutual funds		10,484		—		—		10,484
Equity investments		234		—		—		234
Money market funds		541		—		—		541
Term deposit		—		80,000		—		80,000
Certificate of deposit		—		29,910		—		29,910
Total	$	303,576	$	334,863	$	—	$	638,439

	December 31, 2017
	Level 1		Level 2		Level 3		Total
Corporate bonds	$	—	$	53,943	$	—	$	53,943
Bond and mutual funds		18,402		—		—		18,402
Equity investments		221		—		—		221
Money market funds		569,942		—		—		569,942
Total	$	588,565	$	53,943	$	—	$	642,508

The Company’s Level 2 investments are valued using third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar investments, issuer credit spreads, benchmark investments, prepayment/default projections based on historical data and other observable inputs.

The fair values of the Company’s financial liabilities that are carried at historical cost are as follows (in thousands):

	December 31, 2018
	Level 1		Level 2		Level 3		Total
Lease financing obligations	$	—	$	—	$	98,105	$	98,105

	December 31, 2017
	Level 1		Level 2		Level 3		Total
Lease financing obligations	$	—	$	—	$	98,476	$	98,476

The fair value of the Company’s financial liabilities were derived by using an income approach, which required Level 3 inputs such as discounted estimated future cash flows.

There were no transfers of assets or liabilities between levels for the years ended December 31, 2018, 2017 and 2016.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Balance Sheet Components

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Balance Sheet Components

5.	Balance Sheet Components

Cash and Cash Equivalents

Cash and cash equivalents consisted of the following (in thousands):

	December 31,
	2018		2017
Cash	$	38,783	$	103,716
US treasury notes and bills		49,934		—
Money market funds		541		569,942
Total cash and cash equivalents	$	89,258	$	673,658

Property and Equipment

Property and equipment consisted of the following (in thousands):

	December 31,
	2018			2017
Leasehold improvements	$	101,200		$	93,758
Building shell (Refer to Note 8)		53,880			53,879
Laboratory equipment		16,405			19,497
Machinery		8,382			—
Computer equipment		6,473			6,006
Furniture and fixtures		5,690			5,575
Construction in progress		367			10,402
Total property and equipment	$	192,397		$	189,117
Less: accumulated depreciation		(65,199	)		(59,641	)
Property and equipment, net	$	127,198		$	129,476

Depreciation expense for the years ended December 31, 2018, 2017 and 2016 was $6.6 million, $6.1 million, and $6.0 million, respectively.

Investments

The Company’s investments consist of available-for-sale debt investments, marketable equity investments, term deposit and certificate of deposit. The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s investments by major investments type are summarized in the tables below (in thousands):

	December 31, 2018
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
US treasury notes and bills	$	467,296	$	109	$	(69	)	$	467,336
Term deposit		80,000		—		—			80,000
Certificates of deposit		30,000		—		(90	)		29,910
Bond and mutual funds		10,464		20		—			10,484
Equity investments		125		109		—			234
Total investments	$	587,885	$	238	$	(159	)	$	587,964

	December 31, 2017
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Corporate bonds	$	53,985	$	4	$	(46	)	$	53,943
Bond and mutual funds		17,249		1,153		—			18,402
Equity investments		126		95		—			221
Total investments	$	71,360	$	1,252	$	(46	)	$	72,566

The contractual maturities of the available-for-sale investments and term deposit were as follows (in thousands):

	December 31, 2018
Within one year	$	532,144
After one year through four years		45,102
Total debt investments		577,246
Bond and mutual funds		10,484
Equity investments		234
Total investments	$	587,964

The Company periodically reviews its available-for-sale investments and term deposit for other-than-temporary impairment. The Company considers factors such as the duration, severity and the reason for the decline in value, the potential recovery period and its intent to sell. For debt securities, the Company also considers whether (i) it is more likely than not that the Company will be required to sell the debt securities before recovery of their amortized cost basis, and (ii) the amortized cost basis cannot be recovered as a result of credit losses. During the three years ended December 31, 2018, the Company did not recognize any other-than-temporary impairment loss.

Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	December 31,
	2018		2017
Preclinical and clinical trial accruals	$	35,413	$	32,321
Payroll and related accruals		21,430		18,810
Property taxes and other		1,095		4,201
Professional services		2,648		1,991
Other		5,537		6,458
Total accrued liabilities	$	66,123	$	63,781

Product Development Obligations

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Product Development Obligations

6.	Product Development Obligations

The Technology Development Center of the Republic of Finland (“TEKES”) product development obligations consist of 11 separate advances (each in the form of a note agreement) received by FibroGen Europe between 1996 and 2008 from TEKES. These advances are granted on a project by project basis to fund various product development efforts undertaken by FibroGen Europe only. Each separate note bears interest (not compounded) calculated as one percentage point less than the Bank of Finland rate in effect at the time of the note, but no less than 3.0%.

If the research work funded by TEKES does not result in an economically profitable business or does not meet its technological objectives, TEKES may, on application from FibroGen Europe, forgive each of these loans, including accrued interest, either in full or in part. As of December 31, 2018 and 2017, the Company had $10.8 million and $11.3 million of principal outstanding, respectively, and $6.0 million and $5.9 million of interest accrued, respectively, which were presented in the product development obligations line on the consolidated balance sheets.

The Company is not a guarantor of these loans, and these loans are not repayable by FibroGen Europe until it has distributable funds.

Convertible Note Payable

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Convertible Note Payable

7.	Convertible Note Payable

In January 2013, FibroGen China entered into a $0.6 million convertible promissory note. The note bears simple interest at a rate of two percent (2.00%) per annum, accrued on an annual basis in arrears. The outstanding principal balance and unpaid accrued interest on the note is due and payable upon the earlier of (a) the effectiveness of the initial public offering of FibroGen China or (b) the eight year anniversary of the date of the note. The total outstanding principal balance and unpaid accrued interest on the note will be converted into Series A Preferred Stock of FibroGen China at the option of the lender or by the Company at its discretion. As of December 31, 2018 and 2017, the total outstanding principal balance and accrued interest were $0.7 million and $0.6 million, respectively, and recorded in the other long-term liabilities in the consolidated balance sheets.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Commitments and Contingencies

8.	Commitments and Contingencies

Operating Leases

Future minimum lease payments under all non-cancelable operating lease obligations as of December 31, 2018 are as follows (in thousands):

Year Ending	Operating Leases
2019	$	444
2020		232
2021		25
2022		16
2023		—
Total minimum payments	$	717

Facility Lease Financing Obligations

FibroGen, Inc.

In September 2006, the Company entered into a long-term property lease with Shorenstein Properties LLC (“Alexandria” or “landlord”) providing the Company with 234,249 square feet of space for an initial term of 15 years. Upon signing, a stand-by letter of credit was established in the amount of $7.3 million which has been included in restricted time deposits. Starting the fourth quarter of 2016, on an annual basis, 1/8^th of this letter of credit was released. As a result, the restriction of a $1.0 million was removed, and the amount was reclassified from restricted time deposits to short-term investment during the fourth quarter of each year since 2016. The agreement included an expansion option to occupy part of an adjacent building within 31 months of the lease commencement date of November 20, 2008. In June 2012, the Company gave notice to its landlord that it would not exercise this expansion option, which resulted in a $5.0 million payment liability to the landlord which is being financed over the remaining lease term of its lease.

In connection with this lease, the Company was responsible for approximately 60% of the construction costs for the tenant improvements. The Company is deemed, for accounting purposes only, to be the accounting owner of the entire project including the building shell, even though it is not the legal owner. The balance of the tenant improvements were paid by Alexandria in the form of a tenant improvement allowance of $140.50 per square foot of rentable space, or $32.5 million.

In connection with the Company’s accounting for this transaction, the Company capitalized Alexandria’s costs of constructing the building shell which totaled $50.8 million, and recognized a corresponding lease financing obligation. The Company also recognized, as an additional lease financing obligation, the reimbursements totaling $32.5 million from landlord for tenant improvements since these reimbursements are also deemed to be a financing obligation.

A portion of the monthly lease payment is allocated to land rent and recorded as an operating lease expense and the non-interest portion of the amortized lease payments to the landlord related to rent of the building is applied to the lease financing liability.

FibroGen China

In February 2013, the Company entered into a long-term property lease with Beijing Economic-Technological Development Area (“BDA”) Management Committee for a pilot plant located in Beijing Yizhuang Biomedical Park (“BYBP”) of BDA. The leased space is 4,820 square meters over an eight (8) year term starting February 1, 2013.

In connection with this lease, the Company was responsible for approximately 100% of the construction costs for the tenant improvements. The Company is deemed, for accounting purposes only, to be the accounting owner of the entire project, including the building shell, even though it is not the legal owner.

In connection with the Company’s accounting for this transaction, the Company capitalized BDA Management Committee’s costs of constructing the building shell which totaled $3.1 million, and recognized a corresponding lease financing obligation. The Company also recognized, as an additional lease financing obligation, the reimbursements totaling $0.5 million from BYBP for a rent subsidy since this reimbursement is also deemed to be a financing obligation.

Future minimum lease payments, on a consolidated basis, under the Company’s facility lease financing obligations as of December 31, 2018 are as follows (in thousands):

Year Ending	Lease financing obligations
2019	$	14,379
2020		14,664
2021		14,179
2022		14,335
2023		12,872
Total minimum payments	$	70,429

Apart from the property leases with Alexandria and BDA Management Committee, rent expense for leased facilities under operating lease commitments was $3.1 million, $3.0 million, and $2.8 million for the years ended December 31, 2018, 2017 and 2016, respectively. The Company received sublease income of $3.5 million, $3.9 million, and $3.8 million for the years ended December 31, 2018, 2017 and 2016, respectively, which were recorded as a reduction of research and development expenses and general and administrative expenses for the respective periods.

Indemnification Agreements

The Company enters into standard indemnification arrangements in the ordinary course of business, including for example, service, manufacturing and collaboration agreements. Pursuant to these arrangements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified parties for losses suffered or incurred by the indemnified party, including in connection with intellectual property infringement claims by any third party with respect to its technology. The term of these indemnification agreements is generally perpetual any time after the execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these arrangements is not determinable. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements. As a result, the Company believes the estimated fair value of these arrangements is minimal.

The Company has entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the extent permissible under applicable law.

Equity and Stock-based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Equity and Stock-based Compensation

9.	Equity and Stock-based Compensation

Subsidiary Stock and Non-Controlling Interests

FibroGen Europe

As of December 31, 2018 and 2017, respectively, FibroGen Europe had a total of 42,619,022 shares of Preferred Stock outstanding, of which there were 1,700,845 shares of Series A Preferred Stock, 1,875,000 shares of Series B Preferred Stock, 1,599,503 shares of Series C Preferred Stock, 1,520,141 shares of Series D Preferred Stock, 459,565 shares of Series E Preferred Stock, 5,714,332 shares of Series F Preferred Stock, 9,927,500 shares of Series G Preferred Stock and 19,822,136 shares of Series H Preferred Stock, all of which shares no longer have any right to be exchanged for FibroGen, Inc. Common Stock.

The holders of FibroGen Europe’s shares of Preferred Stock (“Preferred Shares”) have the following rights, preferences and privileges:

Dividend Rights — When the assets of FibroGen Europe are distributed (except for distribution in a liquidation), Preferred Shares shall have the same rights to dividend or other forms of distribution as shares of Common Stock of FibroGen Europe. In the event of a merger, holders of Preferred Shares do not have the right to demand FibroGen Europe to redeem all or part of their Preferred Shares. FibroGen Europe may repurchase shares of Common Stock or Preferred Shares for consideration.

Pre-emptive Right — Preferred Shares shall have pre-emptive subscription right in accordance with the Finnish Limited Liability Companies Act if additional shares are issued, option rights are given, or convertible loan is taken, provided, however, that the foregoing pre-emptive right does not apply to a directed share issue, for which two thirds (2/3) of the voting shares represented at a general meeting of shareholders approve for an important legitimate cause.

Redemption Right — If a Preferred Share can be redeemed by a majority shareholder owning more than ninety percent (90%) of the shares of FibroGen Europe in accordance with the provisions of the Finnish Limited Liability Companies Act, the minority holders of Preferred Shares have the right to request redemption of their shares.

Voting Right — Each share has one vote. Preferred Shares have voting rights only in situations that are specifically provided in the Articles of Association, which include a merger transaction and directed share issue. In addition, Preferred Shares have right to vote in a general shareholder meeting for amending the Articles of Association if the amendment will affect the rights of Preferred Shares.

Conversion Right (1-for-1 basis into Common Stock of FibroGen Europe):

•

Voluntary conversion right: Preferred Shares can be converted into common shares upon the written request of a shareholder provided that the conversion is feasible within the maximum and minimum amounts of shares of classes of FibroGen Europe as set forth in its Articles of Association. Such request can be withdrawn before the notification of conversion is filed with the Finnish Trade Register.

•

Compulsory conversion right: Preferred Shares will be converted into common shares if (i) FibroGen Europe’s shares are listed in a stock exchange or other trading system in the European Economic Area, or (ii) FibroGen Europe’s recombinant collagen and gelatin production technology is being put into commercial use in the area of EU and certain other European states. Commercial use means there is income generated from the first commercial sale of the products incorporating the above mentioned technology and does not include license fees, development financing, milestone payments or income from test products or equipment used in research. The board of directors of FibroGen Europe shall notify the shareholders of the compulsory conversion in writing, and the shareholders shall request to convert their shares within the timeframe provided in the notification. Should the shareholders fail to make the conversion request within the time limit, FibroGen Europe may redeem the shares of such shareholders.

Liquidation Right — In the event of a dissolution of FibroGen Europe, holders of Preferred Shares are entitled to be paid in an amount equal to the subscription price of the shares before any distribution is made to holders of common shares. Among holders of Preferred Shares, holders of shares of Series F Preferred Stock are entitled to be paid in an amount equal to the subscription price of Series F Preferred Stock before any distribution is made to holders of other Preferred Shares.

FibroGen China

FibroGen China had 6,758,000 Series A Preference Shares outstanding as of December 31, 2018 and 2017, respectively. The holders of the FibroGen China Series A Preference Shares have the following rights, preferences and privileges:

Liquidation — In the event of liquidation, dissolution, or winding up of the Company, either voluntary or involuntary, including by means of a merger, the holders of FibroGen China Series A Preference Shares are entitled to be paid an amount equal to the product of the number of shares held by a holder of shares of FibroGen China Series A Preference Shares and the original issue price of $1.00 (subject to equitable adjustment for any stock dividend, combination, split, reclassification, recapitalization) plus all declared and unpaid dividends thereon.

Conversion — Each share of FibroGen China Series A Preference Shares is convertible into the number of fully paid and non-assessable shares of Common Stock of FibroGen China that results from dividing the original issue price by the conversion price in effect at the time of the conversion, subject to adjustments for stock splits, stock dividends, reclassifications and like events. The FibroGen China Series A Preference Shares have a conversion price that is equal to the original issuance price such that the conversion ratio to FibroGen China Common Stock is 1:1 as of all periods presented.

Voting — The holders of FibroGen China Series A Preference Shares are entitled to vote together with the FibroGen China Common Stock holders on all matters submitted for a vote of the stockholders. The holder of each share of FibroGen China Series A Preference Shares has the number of votes equal to the number of shares of FibroGen China Common Stock into which it is convertible.

Dividends — The holders of FibroGen China Series A Preference Shares are entitled to receive cash dividends when and if declared, at a rate of 6%.

Non-Controlling Interests

Non-controlling interest positions related to the issuance of subsidiary stock as described above are reported as a separate component of consolidated equity from the equity attributable to the Company’s stockholders at December 31, 2018 and 2017. In addition, the Company does not allocate losses to the non-controlling interests as the outstanding shares representing the non-controlling interest do not represent a residual equity interest in the subsidiary. Upon the initial public offering and as described above, all eligible FibroGen Europe preferred shares were exchanged for 958,996 shares of FibroGen Common Stock. No other FibroGen Europe shares have the right to be exchanged for FibroGen, Inc. Common Stock.

Common Stock

Each share of Common Stock is entitled to one vote. The holders of Common Stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors, subject to the prior rights of holders of all classes of stock outstanding.

Shares of Common Stock outstanding, shares of stock plans outstanding and shares reserved for future issuance related to stock options and RSUs grant and the Company’s Employee Stock Purchase Plan (“ESPP”) purchases are as follows (in thousands):

	December 31,
	2018		2017
Common stock outstanding		85,432		82,498
Stock options outstanding		10,430		11,550
RSUs outstanding		1,428		1,562
Common stock warrants outstanding		4		4
Shares reserved for future stock options and RSUs grant		6,041		4,190
Shares reserved for future ESPP offering		2,618		2,024
Total shares of common stock reserved		105,953		101,828

Stock Plans

Stock Option and RSU Plans

Under the Company’s Amended and Restated 2005 Stock Plan (“2005 Stock Plan”), the Company may issue shares of Common Stock and options to purchase Common Stock and other forms of equity incentives to employees, directors and consultants. Options granted under the 2005 Stock Plan may be incentive stock options or nonqualified stock options. Incentive stock options (“ISO”) may be granted only to employees and officers of the Company. Nonqualified stock options (“NSO”) and stock purchase rights may be granted to employees, directors and consultants. The board of directors has the authority to determine to whom options will be granted, the number of options, the term and the exercise price. Options are to be granted at an exercise price not less than fair market value for an ISO or an NSO. Options generally vest over four years. Options expire no more than 10 years after date of grant. Upon the effective date of the registration statement related to the Company’s initial public offering, the 2005 Plan was amended to cease the grant of any additional awards thereunder, although the Company will continue to issue common stock upon the exercise of previously granted stock options under the 2005 Plan.

In September 2014, the Company adopted a 2014 Equity Incentive Plan (the “2014 Plan”) which became effective on November 13, 2014. The 2014 Plan is the successor equity compensation plan to the 2005 Plan. The 2014 Plan will terminate on November 12, 2024. The 2014 Plan provides for the grant of incentive stock options, nonqualified stock options, restricted stock awards, stock appreciation rights, performance stock awards, performance cash awards, restricted stock units and other stock awards to employees, directors and consultants. Stock options granted must be at prices not less than 100% of the fair market value at date of grant. Option vesting schedules are determined by the Company at the time of issuance and generally have a four year vesting schedule (25% vesting on the first anniversary of the vesting base date and quarterly thereafter over the next 3 years). Options generally expire ten years from the date of grant unless the optionee is a 10% stockholder, in which case the term will be five years from the date of grant. Unvested options exercised are subject to the Company’s repurchase right. Shares reserved for issuance increases on January 1 of each year commencing on January 1, 2016 and ending on January 1, 2024 by the lesser of (i) the amount equal to 4% of the number of shares issued and outstanding on December 31 immediately prior to the date of increase or (ii) such lower number of shares as may be determined by the board of directors. As of December 31, 2018, the Company has reserved 6,040,725 shares of its common stock that remains unissued for issuance under the 2014 Plan.

Issuance of shares upon share option exercise or share unit conversion is made through issuance of new shares authorized under the plan.

Certain Common Stock option holders have the right to exercise unvested options, subject to a right held by the Company to repurchase the stock, at the original exercise price, in the event of voluntary or involuntary termination of employment of the stockholder. The shares are generally released from repurchase provisions ratably over four years. The Company accounts for the cash received in consideration for the early exercised options as a liability. At December 31, 2018 and 2017, no shares of Common Stock were subject to repurchase by the Company.

Stock option transactions, including forfeited options granted under the 2014 Plan as well as prior plans, are summarized below:

	Shares (In thousands)			Weighted Average Exercise per Share		Weighted Average Remaining Contractual Life (In Years)		Aggregate Intrinsic Value (In thousands)
Outstanding at December 31, 2017		11,550		$	14.82
Granted		1,307			53.64
Exercised		(2,271	)		11.20
Expired		(7	)		5.82
Forfeited		(149	)		30.55
Outstanding at December 31, 2018		10,430			20.25		5.47	$	281,436
Vested and expected to vest, December 31, 2018		10,430			20.25		5.47		281,436
Exercisable at December 31, 2018		7,644		$	13.83		4.47	$	248,206

The total intrinsic value of options exercised during the years ended December 31, 2018, 2017 and 2016 was $97.5 million, $111.9 million, and $17.9 million, respectively.

The following table summarizes RSU activity:

	Shares (In thousands)			Fair Value at Grant
Unvested at December 31, 2017		1,562		$	24.75
Granted		706			53.69
Vested		(727	)		24.70
Forfeited		(113	)		35.12
Unvested at December 31, 2018		1,428		$	38.26

Among the vested RSUs during the year ended December 31, 2017, 432,472 shares were released and issued, while the remaining was withheld for the related payroll taxes. The estimated weighted-average fair value of the awards granted during the years ended December 31, 2018, 2017 and 2016 was $53.69, $26.59 and $19.37, respectively.

ESPP

In September 2014, the Company adopted a 2014 ESPP that became effective on November 13, 2014. The 2014 ESPP is designed to enable eligible employees to periodically purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan or IRS limitations. At the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last day of the offering period. Purchases are accomplished through participation in discrete offering periods. The 2014 ESPP is intended to qualify as an ESPP under Section 423 of the Internal Revenue Code. The Company has reserved 1,600,000 shares of its common stock for issuance under the 2014 ESPP and shares reserved for issuance increases January 1 of each year commencing January 1, 2016 by the lesser of (i) a number of shares equal to 1% of the total number of outstanding shares of common stock on December 31 immediately prior to the date of increase; (ii) 1,200,000 shares or (iii) such number of shares as may be determined by the board of directors. There were 230,317 shares, 250,834 shares and 266,720 shares purchased by employees under the 2014 Purchased Plan for the years ended December 31, 2018, 2017 and 2016, respectively.

The expected term of 2014 ESPP shares is the average of the remaining purchase periods under each offering period.

Stock-Based Compensation

Stock-based compensation expense allocated to research and development and general and administrative expense for the years ended December 31, 2018, 2017 and 2016 was as follows (in thousands):

	Years Ended December 31,
	2018		2017		2016
Research and development	$	30,491	$	21,807	$	19,070
General and administrative		21,651		15,732		13,062
Total stock-based compensation expense	$	52,142	$	37,539	$	32,132

The Company estimates the fair value of stock options using the Black-Scholes option valuation model. The fair value of employee stock options is being amortized on a straight-line basis over the requisite service period of the awards.

Prior to the Company’s initial public offering, the Company, in making its determinations of the fair value of its Common Stock, considered a variety of quantitative and qualitative factors, including (i) net present value of the Company’s projected earnings, (ii) fair market value of the stock of comparable publicly-traded companies, (iii) any third party transactions involving the Company’s convertible preferred stock, (iv) liquidation preferences of the Company’s preferred stock and the likelihood of conversion of the preferred stock, (v) changes in the Company’s business operations, financial condition and results of operations over time, including cash balances and burn-rate, (vi) the status of new product development, and (vii) general financial market conditions. Subsequent to the IPO, the fair market value of common stock is based on the closing price of the Company’s common stock as reported on the NASDAQ Global Select Market on the date of the grant.

The fair value of employee stock options was estimated using the following assumptions:

Expected Term. Expressed as a weighted-average, the expected life of the options is based on the average period the stock options are expected to be outstanding and was based on the Company’s historical information of the option exercise patterns and post-vesting termination behavior as well as contractual terms of the instruments.

Expected Volatility. While the Company considers its historical data regarding the volatility of its Common Stock, the expected volatility is currently based upon the historical volatility of comparable public entities. In evaluating comparable companies, the Company considered factors such as industry, stage of life cycle, size and duration as a public company.

Risk-Free Interest Rate. Expressed as a weighted-average, the risk-free interest rate assumption is based on the U.S. Treasury instruments whose term was consistent with the expected term of the Company’s stock options.

Expected Dividend Yield. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future.

The assumptions used to estimate the fair value of stock options granted and ESPPs using the Black-Scholes option valuation model were as follows:

	Years Ended December 31,
	2018			2017			2016
Stock Options
Expected term (in years)		5.4			5.7			5.3
Expected volatility		67.9	%		71.5	%		69.9	%
Risk-free interest rate		2.7	%		2.2	%		1.4	%
Expected dividend yield		—			—			—
Weighted average estimated fair value	$	32.12		$	16.96		$	11.49

ESPPs
Expected term (in years)	0.5 - 2.0			0.5 - 2.0			0.5 - 2.0
Expected volatility	47.3 - 75.3		%	52.8 - 77.2		%	61.9 - 80.7		%
Risk-free interest rate	0.8 - 2.9		%	0.5 - 1.6		%	0.2 - 1.0		%
Expected dividend yield		—			—			—
Weighted average estimated fair value	$	16.27		$	9.41		$	9.94

As of December 31, 2018, there was $46.6 million of total unrecognized compensation costs, net of estimated forfeitures, related to non-vested stock option awards granted that will be recognized on a straight-line basis over the weighted-average period of 2.24 years. As of December 31, 2018, there was $40.9 million of total unrecognized compensation costs, net of estimated forfeitures, related to non-vested RSUs granted that will be recognized on a straight-line basis over the weighted-average period of 2.40 years.

Warrants

The following warrants to purchase shares of Common Stock were issued in connection with certain facility and equipment lease financing arrangements and are outstanding at December 31, 2018:

Year of Issuance	Number of Shares		Exercise Price per Share		Reason for Issuance	Expiration Date
2000		4,430	$	15.00	Issued in connection with lease agreement	Five years after initial public offering or upon merger or sale of the Company’s assets, whichever occurs first
		4,430

Net Loss Per Share

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Net Loss Per Share

10.	Net Loss Per Share

The following securities were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the three years presented (in thousands):

	Years Ended December 31,
	2018		2017		2016
Employee stock options		10,430		11,550		13,660
RSUs outstanding		1,428		1,562		1,211
Warrants		4		4		4
		11,862		13,116		14,875

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

12.	Income Taxes

The components of loss before income taxes are as follows (in thousands):

	Years Ended December 31,
	2018			2017 *			2016 *
Domestic	$	(38,472	)	$	(80,735	)	$	(25,342	)
Foreign		(47,644	)		(39,819	)		(32,797	)
Loss before provision for income taxes	$	(86,116	)	$	(120,554	)	$	(58,139	)

*	Recast to reflect the adoption of the new revenue standards. See Note 2.

The provision for (benefit from) income taxes consists of the following (in thousands):

	Years Ended December 31,
	2018		2017		2016
Current:
Federal	$	—	$	—	$	—
State		2		2		2
Foreign		302		319		139
Total current		304		321		141
Deferred:
Federal		—		—		(212	)
State		—		—		—
Foreign		—		—		—
Total deferred		—		—		(212	)
Total provision for (benefit from) income taxes	$	304	$	321	$	(71	)

The following is the reconciliation between the statutory federal income tax rate and the Company’s effective tax rate:

	Years Ended December 31,
	2018			2017			2016
Tax at statutory federal rate		21.0	%		34.0	%		34.0	%
State tax		—	%		—	%		—	%
Stock-based compensation expense		14.5	%		18.5	%		(7.9	)%
Change in deferred tax assets due to rate change		—	%		43.9	%		—	%
Change in valuation allowance due to rate change		—	%		(43.9	)%		—	%
Net operating losses not benefitted		(23.2	)%		(43.8	)%		(12.9	)%
Foreign net operating losses not benefitted		(11.6	)%		(6.7	)%		(13.0	)%
Orphan drug credit		0.0	%		(2.0	)%		—	%
Other		(1.1	)%		(0.3	)%		(0.1	)%
Total		(0.4	)%		(0.3	)%		0.1	%

Significant components of the Company’s deferred tax assets are as follows (in thousands):

	December 31,
	2018			2017
Federal and state net operating loss carryforwards	$	91,683		$	71,256
Tax credit carryforwards		45,885			39,488
Foreign net operating loss carryforwards		21,295			15,052
Stock-based compensation		9,281			7,835
Lease obligations		2,511			2,737
Reserves and accruals		6,072			4,851
Deferred revenue		16,454			18,103
Fixed assets		356			—
Other		450			420
Subtotal		193,987			159,742
Less: Valuation allowance		(193,987	)		(159,540	)
Net deferred tax assets		—			202

Fixed assets		—			(181	)
Other		—			(21	)
Net deferred tax liabilities		—			(202	)
Total net deferred tax assets	$	—		$	—

A valuation allowance has been provided to reduce the deferred tax assets to an amount management believes is more likely than not to be realized. Expected realization of the deferred tax assets for which a valuation allowance has not been recognized is based on upon the reversal of existing temporary differences and future taxable income.

The valuation allowance increased by $34.4 million, $30.5 million and $12.3 million for the years ended December 31, 2018, 2017 and 2016, respectively. Due to uncertainty surrounding the realization of the favorable tax attributes in the future tax returns, the Company has established a valuation allowance against its otherwise recognizable net deferred tax assets.

At December 31, 2018, the Company had net operating loss carryforwards available to offset future taxable income of approximately $400.3 million and $148.1 million for federal and state tax purposes, respectively. These carryforwards will begin to expire in 2026 for federal and 2019 for state purposes, if not utilized before these dates. The Company also had foreign net operating loss carryforwards of approximately $86.3 million which expire between 2019 and 2028 if not utilized.

At December 31, 2018, the Company had approximately $46.4 million of federal and $26.3 million of California research and development tax credit and other tax credit carryforwards available to offset future taxable income. The federal credits begin to expire in 2019 and the California research credits have no expiration dates.

On December 22, 2017, the Tax Cuts and Jobs Act (“Tax Act”) was signed into law making significant changes to the Internal Revenue Code. Changes include, but are not limited to, a corporate tax rate decrease from 35% to 21% effective for tax years beginning after December 31, 2017, the transition of U.S international taxation from a worldwide tax system to a territorial system, and a one-time transition tax on the mandatory deemed repatriation of cumulative foreign earnings as. In the fourth quarter of 2018, the Company completed its analysis to determine the effect of the Tax Act and no material adjustments were recognized as of December 31, 2018. Developing interpretations of the provisions of the Tax Act, changes to U.S. Treasury regulations, administrative interpretations or court decisions interpreting the Tax Act in the future periods may require further adjustments to the Company’s analysis.

Due to the adoption of ASU 2016-09 in 2017, the Company recorded a retrospective increase of $19.5 million in the deferred tax assets for previously unrecognized excess tax benefits that existed as of December 31, 2016, and a corresponding increase of $19.5 million in the valuation allowance against these deferred tax assets. In addition, all excess tax benefits and deficiencies are recognized as income tax expense and will result in increased volatility in the Company’s income tax.

Federal and state tax laws impose substantial restrictions on the utilization of net operating loss and credit carryforwards in the event of an “ownership change” for tax purposes, as defined in IRC Section 382. The Company reviewed its stock ownership for year ended December 31, 2018 and concluded no ownership changes occurred which would result in a reduction of its net operating loss or in its research and development credits expiring unused. If additional ownership change occurs, the utilization of net operating loss and credit carryforwards could be significantly reduced.

Uncertain Tax Positions

The Company had unrecognized tax benefits of approximately $28.0 million as of December 31, 2018. Approximately $0.5 million of unrecognized tax benefits, if recognized, would affect the effective tax rate. The interest accrued as of December 31, 2018 and 2017 was immaterial.

A reconciliation of the beginning and ending amounts of unrecognized income tax benefits during the three years ended December 31, 2018 is as follows (in thousands):

	Federal and State
Balance as of December 31, 2015	$	24,213
Decrease due to prior positions		(7,109	)
Increase due to current year position		2,550
Balance as of December 31, 2016		19,654
Increase due to prior positions		303
Increase due to current year position		5,448
Decrease due to U.S. tax rate change		(2,044	)
Balance as of December 31, 2017		23,361
Increase due to prior positions		379
Increase due to current year position		4,216
Balance as of December 31, 2018	$	27,956

Unrecognized tax benefits may change during the next twelve months for items that arise in the ordinary course of business. The Company does not anticipate a material change to its unrecognized tax benefits over the next twelve months that would affect the Company’s effective tax rate.

The Company classifies interest and penalties as a component of tax expense, if any.

The Company files income tax returns in the U.S. federal jurisdiction, U.S. state and other foreign jurisdictions. The U.S. federal and U.S. state taxing authorities may choose to audit tax returns for tax years beyond the statute of limitation period due to significant tax attribute carryforwards from prior years, making adjustments only to carryforward attributes. The foreign statute of limitation generally remains open from 2009 to 2018. The Company is not currently under audit in any tax jurisdiction.

Related Party Transactions

12 Months Ended

Dec. 31, 2018

Related Party Transactions

13.	Related Party Transactions

Astellas is an equity investor in the Company and considered a related party. During the years ended December 31, 2018, 2017 and 2016, the Company recorded revenue related to collaboration agreements with Astellas of $100.0 million, $20.1 million, and $31.3 million, respectively. The related party revenue for the year ended December 31, 2018 included $64.8 million product revenue for API to conduct commercial scale manufacturing validation for roxadustat drug product in anticipation of commercial launch in Japan. See Note 3 and below for details. The related party revenue was recast for each of the years ended December 31, 2017 and 2016 as a result of adoption of the new revenue standards. See Note 2 for details.

During the years ended December 31, 2018, 2017 and 2016, the Company recorded expense related to collaboration agreements with Astellas of $1.5 million, $1.0 million and $6.4 million, respectively.

As of December 31, 2018 and 2017, accounts receivable from Astellas were $47.2 million and $4.0 million, respectively, and amounts due to Astellas were $0.4 million and $0.3 million, respectively. The amounts due are included in accrued liabilities on the consolidated balance sheets. The accounts receivable from Astellas as of December 31, 2018 included $43.8 million related to the delivery of roxadustat API to Astellas during the fourth quarter of 2018. The sale of API was pursuant to the Japan Amendment allowing Astellas to manufacture roxadustat drug product for commercialization in Japan.

Segment and Geographic Information

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Segment and Geographic Information

14.	Segment and Geographic Information

The Company has determined that the chief executive officer is the chief operating decision maker (“CODM”). The CODM reviews financial information presented for the Company’s various clinical trial programs as well as results on a consolidated basis. License revenues and development revenues received are not allocated to various programs for purposes of determining a profit measure and resource allocation decisions are made by the CODM based primarily on consolidated results. As such, the Company has concluded that it operates as one segment. Supplemental enterprise-wide information has been presented below.

Geographic Revenues

Geographic revenues, which are based on the bill-to region, are as follows (in thousands):

	Years Ended December 31,
	2018		2017		2016
Europe	$	112,916	$	110,861	$	151,736
Japan (related party)		100,002		20,111		31,323
All other		40		24		130
Total revenue	$	212,958	$	130,996	$	183,189

Geographic Long-Lived Assets

Property and equipment, net by geographic location are as follows (in thousands):

	December 31,
	2018		2017
United States	$	103,539	$	107,228
China		23,659		22,248
Total property and equipment	$	127,198	$	129,476

Customer Concentration

Substantially all of the Company’s revenues to date have been generated from the following collaboration partners that respectively accounted for more than 10% of the Company’s total revenue and accounts receivable:

	Percentage of Revenue									Percentage of Accounts Receivable
	Years Ended December 31,									December 31,
	2018			2017			2016			2018			2017
Astellas—Related party		47	%		15	%		17	%		74	%		47	%
AstraZeneca		53	%		85	%		83	%		26	%		53	%

Schedule II - Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2018

Valuation And Qualifying Accounts [Abstract]

Schedule II - Valuation and Qualifying Accounts

Schedule II: Valuation and Qualifying Accounts

(in thousands)

			Charged		Charged
	Balance at		(Credited)		to Other
	Beginning of		to Statement		Accounts -		Deductions,		Balance at
	Year		of Operation		Equity		Net		End of Year
Valuation allowances for deferred tax assets
Year ended December 31, 2018	$	159,540	$	34,447	$	—	$	—	$	193,987
Year ended December 31, 2017	$	128,995	$	11,039	$	19,506	$	—	$	159,540
Year ended December 31, 2016	$	116,718	$	12,277	$	—	$	—	$	128,995

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Basis of Presentation

The Company operates in one segment — the discovery, development and commercialization of novel therapeutics to treat serious unmet medical needs.

Foreign Currency Translation

Use of Estimates

Concentration of Credit Risk and Other Risks and Uncertainties

	December 31,
	2018			2017
Astellas Pharma Inc. (“Astellas”)—Related party		74	%		47	%
AstraZeneca AB (“AstraZeneca”)		26	%		53	%

Cash, Cash Equivalents and Restricted Time Deposits

Investments

Fair Value of Financial Instruments

Property and Equipment

Impairment of Long-Lived Assets

Revenue Recognition

Substantially all of the Company’s revenues to date have been generated from its collaboration agreements.

Research and Development Expenses

Clinical Trial Accruals

General and Administrative Expenses

Income Taxes

The Company includes interest and penalties related to unrecognized tax benefits within income tax expense in the Consolidated Statements of Operations.

Stock-Based Compensation

The fair value of employee stock options was estimated using the following assumptions:

Expected Dividend Yield. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future.

Comprehensive Income (Loss)

Recently Issued and Adopted Accounting Guidance

New Revenue Standards

Select line items from the Company’s consolidated statement of operations and balance sheet, which reflect the adoption of the new revenue standards are as follows (in thousands):

	Year Ended December 31, 2017									Year Ended December 31, 2016
	As Previously Reported			New Revenue Standards Adjustment			As Recast			As Previously Reported			New Revenue Standards Adjustment			As Recast
Statement of Operations
License revenue	$	96,056		$	(86,123	)	$	9,933		$	137,352		$	(86,745	)	$	50,607
Development and other revenue		29,612			91,451			121,063			42,225			90,357			132,582
Total revenue		125,668			5,328			130,996			179,577			3,612			183,189
Net loss		(126,203	)		5,328			(120,875	)		(61,680	)		3,612			(58,068	)
Net loss per share - basic and diluted	$	(1.73	)	$	0.07		$	(1.66	)	$	(0.98	)	$	0.05		$	(0.93	)

										December 31, 2017
										As Previously Reported			New Revenue Standards Adjustment			As Recast
Balance Sheet
Deferred revenue, current										$	7,968		$	8,702		$	16,670
Deferred revenue, net of current											112,231			26,010			138,241
Accumulated deficit											(595,945	)		(34,712	)		(630,657	)

The adoption of the new revenue standards also resulted in the following changes in the accumulated deficit as of December 31, 2016 and 2015:

	As Previously Reported			New Revenue Standards Adjustment			As Recast
Accumulated Deficit
As of December 31, 2016	$	(469,742	)	$	(40,040	)	$	(509,782	)
As of December 31, 2015	$	(408,062	)	$	(43,652	)	$	(451,714	)

ASU 2016-01

	Accumulated Other Comprehensive Loss			Accumulated Deficit
Balance at December 31, 2017	$	(1,795	)	$	(630,657	)	*
Impact of change in accounting principle upon adoption of ASU 2016-01		(1,250	)		1,250
Opening balance as of January 1, 2018	$	(3,045	)	$	(629,407	)

*	Recast to reflect the adoption of the new revenue standards. See above.

The adoption of this guidance had no impact to the Company’s consolidated statement of cash flows for the year ended December 31, 2018.

ASU 2017-09

ASU 2016-16

Recently Issued Accounting Guidance Not Yet Adopted

Collaboration Arrangements

Accounting for the Astellas Agreements

The promised services that were analyzed, along with their general timing of satisfaction and recognition as revenue, are as follows:

(1)

(2)

(3)	License to the Company’s technology developed during the term of the agreement and development (referred to as “when and if available”) and information sharing services. These promises are generally satisfied throughout the term of the agreements.

(4)	Manufacturing of clinical supplies of products. This promise is satisfied as supplies for clinical product are delivered for use in the Company’s clinical trial programs during the development period, or pre-commercialization period.

(5)	Committee service. This promise is satisfied throughout the course of the agreements as meetings are attended.

(6)

Accounting for the AstraZeneca Agreements

1.	While the two agreements were largely negotiated separately, those negotiations proceeded concurrently, and were intended to be completed contemporaneously, presuming AstraZeneca decided to proceed with licenses in all regions available.

Promised services that were not distinct have been combined with other promised services to form a distinct bundle of promised services, with revenue being recognized on the bundle of services rather than the individual promised services. There are no right-of-return provisions for the delivered items in the AstraZeneca agreements.

U.S./RoW Agreement:

The promised services that were analyzed, along with their general timing of satisfaction and recognition as revenue, are as follows:

(1)

(2)

(3)	Manufacturing of clinical supplies of products. This promise is satisfied as supplies for clinical product are delivered for use in the Company’s clinical trial programs during the development period, or pre-commercialization period.

(4)	Information sharing and committee service. These promises are satisfied throughout the course of the agreement as services are provided.

(5)

China Agreement:

The performance obligation that were analyzed, along with their general timing of satisfaction and recognition as revenue, are as follows:

•

Product Revenue

Other Revenues

Other revenues consist primarily of collagen material sold for research purposes. Other revenues were immaterial for each of the three years ended December 31, 2018.

Deferred Revenue

Fair Value Measurements

Level 1: Quoted prices in active markets for identical assets or liabilities.

Level 2: Observable inputs other than quoted prices in active markets for identical assets or liabilities.

Level 3: Unobservable inputs.

Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policy [Line Items]

Schedule of Significant Balance of Accounts Receivable

The Company has not experienced any loss on its deposits of cash and cash equivalents. Included in current assets are significant balances of accounts receivable as follows:

	December 31,
	2018			2017
Astellas Pharma Inc. (“Astellas”)—Related party		74	%		47	%
AstraZeneca AB (“AstraZeneca”)		26	%		53	%

Schedule of Adoption of New Revenue Standards

Select line items from the Company’s consolidated statement of operations and balance sheet, which reflect the adoption of the new revenue standards are as follows (in thousands):

	Year Ended December 31, 2017									Year Ended December 31, 2016
	As Previously Reported			New Revenue Standards Adjustment			As Recast			As Previously Reported			New Revenue Standards Adjustment			As Recast
Statement of Operations
License revenue	$	96,056		$	(86,123	)	$	9,933		$	137,352		$	(86,745	)	$	50,607
Development and other revenue		29,612			91,451			121,063			42,225			90,357			132,582
Total revenue		125,668			5,328			130,996			179,577			3,612			183,189
Net loss		(126,203	)		5,328			(120,875	)		(61,680	)		3,612			(58,068	)
Net loss per share - basic and diluted	$	(1.73	)	$	0.07		$	(1.66	)	$	(0.98	)	$	0.05		$	(0.93	)

										December 31, 2017
										As Previously Reported			New Revenue Standards Adjustment			As Recast
Balance Sheet
Deferred revenue, current										$	7,968		$	8,702		$	16,670
Deferred revenue, net of current											112,231			26,010			138,241
Accumulated deficit											(595,945	)		(34,712	)		(630,657	)

Schedule of Impacts to Accumulated Other Comprehensive Loss and Accumulated Deficit Upon Adoption of Guidance

The impacts to the Company’s accumulated other comprehensive loss and accumulated deficit upon adoption of this guidance are as follows (in thousands):

	Accumulated Other Comprehensive Loss			Accumulated Deficit
Balance at December 31, 2017	$	(1,795	)	$	(630,657	)	*
Impact of change in accounting principle upon adoption of ASU 2016-01		(1,250	)		1,250
Opening balance as of January 1, 2018	$	(3,045	)	$	(629,407	)

*	Recast to reflect the adoption of the new revenue standards. See above.

Accumulated Deficit [Member]

Accounting Policy [Line Items]

Schedule of Adoption of New Revenue Standards

The adoption of the new revenue standards also resulted in the following changes in the accumulated deficit as of December 31, 2016 and 2015:

	As Previously Reported			New Revenue Standards Adjustment			As Recast
Accumulated Deficit
As of December 31, 2016	$	(469,742	)	$	(40,040	)	$	(509,782	)
As of December 31, 2015	$	(408,062	)	$	(43,652	)	$	(451,714	)

Collaboration Agreements (Tables)

12 Months Ended

Dec. 31, 2018

Japan [Member]

Summary of Revenue Recognized under Agreement

Amounts recognized as revenue under the Japan Agreement were as follows (in thousands):

		Years Ended December 31,
Agreement	Performance Obligation	2018		2017 *		2016 *
Japan	License revenue	$	14,323	$	—	$	9,548
	Development revenue	$	2,400	$	1,588	$	4,288

*	Recast to reflect the adoption of the new revenue standards. See Note 2.

Transaction Price Related to Consideration Received and Accounts Receivable Allocated to Performance Obligations along with Associated Deferred Revenue

Japan Agreement	Cumulative Revenue Through December 31, 2018		Deferred Revenue at December 31, 2018		Total Consideration Through December 31, 2018
License	$	74,089	$	—	$	74,089
Development revenue		13,908		286		14,194
Total license and development revenue	$	87,997	$	286	$	88,283

Europe [Member]

Summary of Revenue Recognized under Agreement

Amounts recognized as revenue under the Europe Agreement were as follows (in thousands):

		Years Ended December 31,
Agreement	Performance Obligation	2018		2017 *		2016 *
Europe	License revenue	$	—	$	—	$	—
	Development revenue	$	18,503	$	18,523	$	17,487

Recast to reflect the adoption of the new revenue standards. See Note 2.

Transaction Price Related to Consideration Received and Accounts Receivable Allocated to Performance Obligations along with Associated Deferred Revenue

Europe Agreement	Cumulative Revenue Through December 31, 2018		Deferred Revenue at December 31, 2018		Total Consideration Through December 31, 2018
License	$	370,481	$	—	$	370,481
Development revenue		202,836		3,225		206,061
Total license and development revenue	$	573,317	$	3,225	$	576,542

U.S./RoW and China [Member]

Summary of Revenue Recognized under Agreement

Amounts recognized as revenue under the U.S./RoW and China Agreements were as follows (in thousands):

		Years Ended December 31,
Agreement	Performance Obligation	2018		2017 *		2016 *
U.S. / RoW and China	License revenue	$	7,946	$	9,933	$	41,059
	Development revenue	$	104,970	$	100,928	$	110,677
	China performance obligation	$	—	$	—	$	—

*	Recast to reflect the adoption of the new revenue standards. See Note 2.

Transaction Price Related to Consideration Received and Accounts Receivable Allocated to Performance Obligations along with Associated Deferred Revenue

U.S. / RoW and China Agreements	Cumulative Revenue Through December 31, 2018		Deferred Revenue at December 31, 2018		Total Consideration Through December 31, 2018
License	$	294,163	$	—	$	294,163
Co-development, information sharing & committee services		408,637		20,521		429,158
China performance obligation		—		125,848		125,848
Total license and development revenue	$	702,800	$	146,369	$	849,169

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair Values of Financial Assets Measured on Recurring Basis

The fair values of the Company’s financial assets that are measured on a recurring basis are as follows (in thousands):

	December 31, 2018
	Level 1		Level 2		Level 3		Total
US treasury notes and bills	$	292,317	$	224,953	$	—	$	517,270
Bond and mutual funds		10,484		—		—		10,484
Equity investments		234		—		—		234
Money market funds		541		—		—		541
Term deposit		—		80,000		—		80,000
Certificate of deposit		—		29,910		—		29,910
Total	$	303,576	$	334,863	$	—	$	638,439

	December 31, 2017
	Level 1		Level 2		Level 3		Total
Corporate bonds	$	—	$	53,943	$	—	$	53,943
Bond and mutual funds		18,402		—		—		18,402
Equity investments		221		—		—		221
Money market funds		569,942		—		—		569,942
Total	$	588,565	$	53,943	$	—	$	642,508

Fair Values of Financial Liabilities Carried at Historical Cost

The fair values of the Company’s financial liabilities that are carried at historical cost are as follows (in thousands):

	December 31, 2018
	Level 1		Level 2		Level 3		Total
Lease financing obligations	$	—	$	—	$	98,105	$	98,105

	December 31, 2017
	Level 1		Level 2		Level 3		Total
Lease financing obligations	$	—	$	—	$	98,476	$	98,476

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Schedule of Cash and Cash Equivalents

Cash and cash equivalents consisted of the following (in thousands):

	December 31,
	2018		2017
Cash	$	38,783	$	103,716
US treasury notes and bills		49,934		—
Money market funds		541		569,942
Total cash and cash equivalents	$	89,258	$	673,658

Schedule of Property and Equipment

Property and equipment consisted of the following (in thousands):

	December 31,
	2018			2017
Leasehold improvements	$	101,200		$	93,758
Building shell (Refer to Note 8)		53,880			53,879
Laboratory equipment		16,405			19,497
Machinery		8,382			—
Computer equipment		6,473			6,006
Furniture and fixtures		5,690			5,575
Construction in progress		367			10,402
Total property and equipment	$	192,397		$	189,117
Less: accumulated depreciation		(65,199	)		(59,641	)
Property and equipment, net	$	127,198		$	129,476

Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Investments

	December 31, 2018
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
US treasury notes and bills	$	467,296	$	109	$	(69	)	$	467,336
Term deposit		80,000		—		—			80,000
Certificates of deposit		30,000		—		(90	)		29,910
Bond and mutual funds		10,464		20		—			10,484
Equity investments		125		109		—			234
Total investments	$	587,885	$	238	$	(159	)	$	587,964

	December 31, 2017
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Corporate bonds	$	53,985	$	4	$	(46	)	$	53,943
Bond and mutual funds		17,249		1,153		—			18,402
Equity investments		126		95		—			221
Total investments	$	71,360	$	1,252	$	(46	)	$	72,566

Summary of Contractual Maturities Available-for-Sale Investments and Term Deposit

The contractual maturities of the available-for-sale investments and term deposit were as follows (in thousands):

	December 31, 2018
Within one year	$	532,144
After one year through four years		45,102
Total debt investments		577,246
Bond and mutual funds		10,484
Equity investments		234
Total investments	$	587,964

Schedule of Accrued Liabilities

Accrued liabilities consisted of the following (in thousands):

	December 31,
	2018		2017
Preclinical and clinical trial accruals	$	35,413	$	32,321
Payroll and related accruals		21,430		18,810
Property taxes and other		1,095		4,201
Professional services		2,648		1,991
Other		5,537		6,458
Total accrued liabilities	$	66,123	$	63,781

Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

Commitments And Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments Under all Non-Cancelable Operating Lease Obligations

Future minimum lease payments under all non-cancelable operating lease obligations as of December 31, 2018 are as follows (in thousands):

Year Ending	Operating Leases
2019	$	444
2020		232
2021		25
2022		16
2023		—
Total minimum payments	$	717

Schedule of Future Minimum Lease Payments on Consolidated Basis Under Company's Facility Financing Lease Obligations

Future minimum lease payments, on a consolidated basis, under the Company’s facility lease financing obligations as of December 31, 2018 are as follows (in thousands):

Year Ending	Lease financing obligations
2019	$	14,379
2020		14,664
2021		14,179
2022		14,335
2023		12,872
Total minimum payments	$	70,429

Equity and Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Common Stock Reserved for Future Issuance

	December 31,
	2018		2017
Common stock outstanding		85,432		82,498
Stock options outstanding		10,430		11,550
RSUs outstanding		1,428		1,562
Common stock warrants outstanding		4		4
Shares reserved for future stock options and RSUs grant		6,041		4,190
Shares reserved for future ESPP offering		2,618		2,024
Total shares of common stock reserved		105,953		101,828

Summary of Stock Option Transactions

Stock option transactions, including forfeited options granted under the 2014 Plan as well as prior plans, are summarized below:

	Shares (In thousands)			Weighted Average Exercise per Share		Weighted Average Remaining Contractual Life (In Years)		Aggregate Intrinsic Value (In thousands)
Outstanding at December 31, 2017		11,550		$	14.82
Granted		1,307			53.64
Exercised		(2,271	)		11.20
Expired		(7	)		5.82
Forfeited		(149	)		30.55
Outstanding at December 31, 2018		10,430			20.25		5.47	$	281,436
Vested and expected to vest, December 31, 2018		10,430			20.25		5.47		281,436
Exercisable at December 31, 2018		7,644		$	13.83		4.47	$	248,206

Summary of RSU Activity

The following table summarizes RSU activity:

	Shares (In thousands)			Fair Value at Grant
Unvested at December 31, 2017		1,562		$	24.75
Granted		706			53.69
Vested		(727	)		24.70
Forfeited		(113	)		35.12
Unvested at December 31, 2018		1,428		$	38.26

Schedule of Allocated Stock-Based Compensation Expense

Stock-based compensation expense allocated to research and development and general and administrative expense for the years ended December 31, 2018, 2017 and 2016 was as follows (in thousands):

	Years Ended December 31,
	2018		2017		2016
Research and development	$	30,491	$	21,807	$	19,070
General and administrative		21,651		15,732		13,062
Total stock-based compensation expense	$	52,142	$	37,539	$	32,132

Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Employee Stock Purchase Plans

The assumptions used to estimate the fair value of stock options granted and ESPPs using the Black-Scholes option valuation model were as follows:

	Years Ended December 31,
	2018			2017			2016
Stock Options
Expected term (in years)		5.4			5.7			5.3
Expected volatility		67.9	%		71.5	%		69.9	%
Risk-free interest rate		2.7	%		2.2	%		1.4	%
Expected dividend yield		—			—			—
Weighted average estimated fair value	$	32.12		$	16.96		$	11.49

ESPPs
Expected term (in years)	0.5 - 2.0			0.5 - 2.0			0.5 - 2.0
Expected volatility	47.3 - 75.3		%	52.8 - 77.2		%	61.9 - 80.7		%
Risk-free interest rate	0.8 - 2.9		%	0.5 - 1.6		%	0.2 - 1.0		%
Expected dividend yield		—			—			—
Weighted average estimated fair value	$	16.27		$	9.41		$	9.94

Schedule of Warrants to Purchase Shares of Common Stock

The following warrants to purchase shares of Common Stock were issued in connection with certain facility and equipment lease financing arrangements and are outstanding at December 31, 2018:

Year of Issuance	Number of Shares		Exercise Price per Share		Reason for Issuance	Expiration Date
2000		4,430	$	15.00	Issued in connection with lease agreement	Five years after initial public offering or upon merger or sale of the Company’s assets, whichever occurs first
		4,430

- Definition

Tabular disclosure of warrants or rights issued. Warrants and rights outstanding are derivative securities that give the holder the right to purchase securities (usually equity) from the issuer at a specific price within a certain time frame. Warrants are often included in a new debt issue to entice investors by a higher return potential. The main difference between warrants and call options is that warrants are issued and guaranteed by the company, whereas options are exchange instruments and are not issued by the company. Also, the lifetime of a warrant is often measured in years, while the lifetime of a typical option is measured in months. Disclose the title of issue of securities called for by warrants and rights outstanding, the aggregate amount of securities called for by warrants and rights outstanding, the date from which the warrants or rights are exercisable, and the price at which the warrant or right is exercisable.

+ References + Details

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Schedule of Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share

The following securities were excluded from the calculation of diluted net loss per share because their effect would have been anti-dilutive for the three years presented (in thousands):

	Years Ended December 31,
	2018		2017		2016
Employee stock options		10,430		11,550		13,660
RSUs outstanding		1,428		1,562		1,211
Warrants		4		4		4
		11,862		13,116		14,875

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of Components of Loss Before Income Taxes

The components of loss before income taxes are as follows (in thousands):

	Years Ended December 31,
	2018			2017 *			2016 *
Domestic	$	(38,472	)	$	(80,735	)	$	(25,342	)
Foreign		(47,644	)		(39,819	)		(32,797	)
Loss before provision for income taxes	$	(86,116	)	$	(120,554	)	$	(58,139	)

Schedule of Components of Provision For (Benefit From) Income Taxes

The provision for (benefit from) income taxes consists of the following (in thousands):

	Years Ended December 31,
	2018		2017		2016
Current:
Federal	$	—	$	—	$	—
State		2		2		2
Foreign		302		319		139
Total current		304		321		141
Deferred:
Federal		—		—		(212	)
State		—		—		—
Foreign		—		—		—
Total deferred		—		—		(212	)
Total provision for (benefit from) income taxes	$	304	$	321	$	(71	)

Schedule of Reconciliation Between Statutory Federal Income Tax Rate and Effective Tax Rate

The following is the reconciliation between the statutory federal income tax rate and the Company’s effective tax rate:

	Years Ended December 31,
	2018			2017			2016
Tax at statutory federal rate		21.0	%		34.0	%		34.0	%
State tax		—	%		—	%		—	%
Stock-based compensation expense		14.5	%		18.5	%		(7.9	)%
Change in deferred tax assets due to rate change		—	%		43.9	%		—	%
Change in valuation allowance due to rate change		—	%		(43.9	)%		—	%
Net operating losses not benefitted		(23.2	)%		(43.8	)%		(12.9	)%
Foreign net operating losses not benefitted		(11.6	)%		(6.7	)%		(13.0	)%
Orphan drug credit		0.0	%		(2.0	)%		—	%
Other		(1.1	)%		(0.3	)%		(0.1	)%
Total		(0.4	)%		(0.3	)%		0.1	%

Schedule of Significant Components of Deferred Tax Assets

Significant components of the Company’s deferred tax assets are as follows (in thousands):

	December 31,
	2018			2017
Federal and state net operating loss carryforwards	$	91,683		$	71,256
Tax credit carryforwards		45,885			39,488
Foreign net operating loss carryforwards		21,295			15,052
Stock-based compensation		9,281			7,835
Lease obligations		2,511			2,737
Reserves and accruals		6,072			4,851
Deferred revenue		16,454			18,103
Fixed assets		356			—
Other		450			420
Subtotal		193,987			159,742
Less: Valuation allowance		(193,987	)		(159,540	)
Net deferred tax assets		—			202

Fixed assets		—			(181	)
Other		—			(21	)
Net deferred tax liabilities		—			(202	)
Total net deferred tax assets	$	—		$	—

Schedule of Reconciliation of the Beginning and Ending Amounts of Unrecognized Income Tax Benefits

A reconciliation of the beginning and ending amounts of unrecognized income tax benefits during the three years ended December 31, 2018 is as follows (in thousands):

	Federal and State
Balance as of December 31, 2015	$	24,213
Decrease due to prior positions		(7,109	)
Increase due to current year position		2,550
Balance as of December 31, 2016		19,654
Increase due to prior positions		303
Increase due to current year position		5,448
Decrease due to U.S. tax rate change		(2,044	)
Balance as of December 31, 2017		23,361
Increase due to prior positions		379
Increase due to current year position		4,216
Balance as of December 31, 2018	$	27,956

Segment and Geographic Information (Tables)

12 Months Ended

Dec. 31, 2018

Segment Reporting [Abstract]

Schedule of Revenue by Geographic Area

Geographic revenues, which are based on the bill-to region, are as follows (in thousands):

	Years Ended December 31,
	2018		2017		2016
Europe	$	112,916	$	110,861	$	151,736
Japan (related party)		100,002		20,111		31,323
All other		40		24		130
Total revenue	$	212,958	$	130,996	$	183,189

Schedule of Long Lived Assets by Geographic Area

Property and equipment, net by geographic location are as follows (in thousands):

	December 31,
	2018		2017
United States	$	103,539	$	107,228
China		23,659		22,248
Total property and equipment	$	127,198	$	129,476

Schedule of Customer Concentration by Collaboration Partners

	Percentage of Revenue									Percentage of Accounts Receivable
	Years Ended December 31,									December 31,
	2018			2017			2016			2018			2017
Astellas—Related party		47	%		15	%		17	%		74	%		47	%
AstraZeneca		53	%		85	%		83	%		26	%		53	%

The Company - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Aug. 24, 2017	Apr. 11, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Description [Line Items]
Net proceeds from offering			$ 29,847	$ 34,910	$ 9,881
Follow On Offering
Business Description [Line Items]
Common stock shares sold	9,200,000	5,228,750
Public offering price	$ 40.75	$ 22.95
Net proceeds from offering	$ 356,200	$ 115,100
Underwriting discounts and commissions	18,700	4,900
Offering expenses	$ 400	$ 600

Summary of Significant Accounting Policies - Additional Information (Detail)		12 Months Ended
	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($) Segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016
Accounting Policy [Line Items]
Number of operating segment \| Segment		1
Highly liquid investment maturity period		three months or less
Restricted time deposits		$ 4,145,000	$ 5,181,000
Cash and cash equivalents		$ 89,258,000	$ 673,658,000
Short term investments Maturity		12 months
Long term Investments Maturity		12 months
Impairment of long-lived assets		$ 0
U.S. federal statutory income tax rate		21.00%	34.00%	34.00%
ASU 2018-02 [Member] \| Accumulated Deficit [Member] \| Subsequent Event [Member]
Accounting Policy [Line Items]
Cumulative effect on accumulated deficit	$ 600,000
Minimum [Member] \| ASU 2016-02 [Member]
Accounting Policy [Line Items]
Right-of-use assets		$ 47,000,000
Lease liabilities		$ 57,000,000
Minimum [Member] \| Computer Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life		3 years
Minimum [Member] \| Laboratory Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life		3 years
Minimum [Member] \| Furniture and Fixtures [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life		3 years
Maximum [Member]
Accounting Policy [Line Items]
U.S. federal statutory income tax rate			35.00%
Maximum [Member] \| ASU 2016-02 [Member]
Accounting Policy [Line Items]
Right-of-use assets		$ 62,000,000
Lease liabilities		$ 67,000,000
Maximum [Member] \| Computer Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life		5 years
Maximum [Member] \| Laboratory Equipment [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life		5 years
Maximum [Member] \| Furniture and Fixtures [Member]
Accounting Policy [Line Items]
Property and equipment estimated useful life		5 years
Foreign subsidiaries [Member]
Accounting Policy [Line Items]
Cash and cash equivalents		$ 21,900,000

Summary of Significant Accounting Policies - Schedule of Significant Balance of Accounts Receivable (Detail) - Accounts Receivable [Member] - Credit Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Astellas Agreement [Member]
Accounting Policy [Line Items]
Concentration risk, percentage	74.00%	47.00%
AstraZeneca Agreements [Member]
Accounting Policy [Line Items]
Concentration risk, percentage	26.00%	53.00%

Summary of Significant Accounting Policies - Schedule of Adoption of New Revenue Standards (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Operations
Total revenue	$ 212,958	$ 130,996	$ 183,189
Net loss	$ (86,420)	$ (120,875)	$ (58,068)
Net loss per share - basic and diluted	$ (1.03)	$ (1.66)	$ (0.93)
Balance Sheet
Deferred revenue	$ 13,771	$ 16,670
Deferred revenue, net of current	136,109	138,241
Accumulated deficit	(715,827)	(630,657)	$ (509,782)	$ (451,714)
License Revenue [Member]
Statement of Operations
Total revenue	22,269	9,933	50,607
Development and Other Revenue [Member]
Statement of Operations
Total revenue	$ 125,913	121,063	132,582
As Previously Reported [Member] \| ASU 2014-09 [Member]
Statement of Operations
Total revenue		125,668	179,577
Net loss		$ (126,203)	$ (61,680)
Net loss per share - basic and diluted		$ (1.73)	$ (0.98)
Balance Sheet
Deferred revenue		$ 7,968
Deferred revenue, net of current		112,231
Accumulated deficit		(595,945)	$ (469,742)	(408,062)
As Previously Reported [Member] \| License Revenue [Member] \| ASU 2014-09 [Member]
Statement of Operations
Total revenue		96,056	137,352
As Previously Reported [Member] \| Development and Other Revenue [Member] \| ASU 2014-09 [Member]
Statement of Operations
Total revenue		29,612	42,225
New Revenue Standards Adjustment [Member] \| ASU 2014-09 [Member]
Statement of Operations
Total revenue		5,328	3,612
Net loss		$ 5,328	$ 3,612
Net loss per share - basic and diluted		$ 0.07	$ 0.05
Balance Sheet
Deferred revenue		$ 8,702
Deferred revenue, net of current		26,010
Accumulated deficit		(34,712)	$ (40,040)	$ (43,652)
New Revenue Standards Adjustment [Member] \| License Revenue [Member] \| ASU 2014-09 [Member]
Statement of Operations
Total revenue		(86,123)	(86,745)
New Revenue Standards Adjustment [Member] \| Development and Other Revenue [Member] \| ASU 2014-09 [Member]
Statement of Operations
Total revenue		$ 91,451	$ 90,357

Summary of Significant Accounting Policies - Schedule of Adoption of New Revenue Standards Changes in Accumulated Deficit (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accumulated deficit	$ (715,827)	$ (630,657)	$ (509,782)	$ (451,714)
As Previously Reported [Member] \| ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accumulated deficit		(595,945)	(469,742)	(408,062)
New Revenue Standards Adjustment [Member] \| ASU 2014-09 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accumulated deficit		$ (34,712)	$ (40,040)	$ (43,652)

Summary of Significant Accounting Policies - Schedule of Impacts to Accumulated Other Comprehensive Loss and Accumulated Deficit Upon Adoption of Guidance (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policy [Line Items]
Accumulated other comprehensive loss	$ (2,281)		$ (1,795)
Accumulated deficit	$ (715,827)		$ (630,657)	$ (509,782)	$ (451,714)
ASU 2016-01 [Member]
Accounting Policy [Line Items]
Accumulated other comprehensive loss		$ (3,045)
Accumulated deficit		(629,407)
Impact of change in accounting principle upon adoption of ASU 2016-01 [Member] \| ASU 2016-01 [Member]
Accounting Policy [Line Items]
Accumulated other comprehensive loss		(1,250)
Accumulated deficit		$ 1,250

Collaboration Agreements - Astellas Agreements - Additional Information (Detail) - Astellas Agreement [Member] - USD ($) $ in Millions	1 Months Ended			3 Months Ended	12 Months Ended	35 Months Ended	45 Months Ended
	Dec. 31, 2018	Apr. 30, 2006	Jun. 30, 2005	Jun. 30, 2018	Dec. 31, 2018	Feb. 28, 2009	Feb. 28, 2009
Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received							$ 40.1
Development and regulatory approval milestones			$ 117.5
Commercial sales milestone			$ 15.0
Additional consideration based on net sales description					Low 20% range
Consideration associated with milestone included in transaction price				$ 15.0
Contract with customer liability, revenue recognized	$ 43.9			$ 20.9
Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received						$ 320.0
Development and regulatory approval milestones		$ 425.0
Additional consideration based on net sales description					0
Percentage of joint development costs committed to fund		50.00%
Estimated joint development extended service period					2023

Collaboration Agreements - AstraZeneca Agreements - Additional Information 1 (Detail) - AstraZeneca Agreements [Member] - USD ($) $ in Millions				3 Months Ended			12 Months Ended
	Dec. 29, 2018	Dec. 17, 2018	Jul. 30, 2013	Dec. 31, 2018	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2015
U.S./RoW [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Expected upfront, non-contingent and time-based payments			$ 374.0
Development and regulatory approval milestones			550.0
Commercial sales milestone			325.0
Shared development costs								$ 233.0
Additional consideration based on net sales description							Low 20% range
U.S./RoW [Member] \| FibroGen, Inc. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shared development costs								$ 116.5
China [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development and regulatory approval milestones			161.0
Commercial sales milestone			167.5
Proceeds from upfront payments			28.2
Contingent payment			$ 20.0
Estimated joint development service period						2018
Estimated joint development extended service period						2020	2024
Milestone payment, revenue recognition	$ 6.0	$ 6.0		$ 9.9	$ 15.0		$ 12.0

Collaboration Agreements - Accounting for the Astellas Agreements - Additional Information 2 (Detail)	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Manufacturing commercial supplies of products, revenue recognized	$ 212,958,000	$ 130,996,000	$ 183,189,000
Astellas Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Co-development services, currently estimated continuation year	2023
Astellas Agreement [Member] \| Manufacturing Commercial Supplies of Products [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Manufacturing commercial supplies of products, revenue recognized	$ 0
Astellas Agreement [Member] \| Minimum [Member] \| Measurement Input Discount Rate [Member] \| Discounted Cash Flow [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Discount rate applied	17.5
Astellas Agreement [Member] \| Maximum [Member] \| Measurement Input Discount Rate [Member] \| Discounted Cash Flow [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Discount rate applied	20.0
Astellas Agreement [Member] \| Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-contingent upfront payments received	$ 40,100,000
Variable consideration related to payments for milestones considered probable of being achieved	37,500,000
Variable consideration related to co-development billings	12,100,000
Provision for co-development services	0
Astellas Agreement [Member] \| Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-contingent upfront payments received	320,000,000
Variable consideration related to payments for milestones considered probable of being achieved	90,000,000
Variable consideration related to co-development billings	$ 180,900,000

Collaboration Agreements - Accounting for the AstraZeneca Agreements - Additional Information 3 (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Manufacturing commercial supplies of products, revenue recognized	$ 212,958,000	$ 130,996,000	$ 183,189,000
AstraZeneca Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty rate against projected net revenues	40.00%
Co-development services, currently estimated continuation year	2024
AstraZeneca Agreements [Member] \| Manufacturing Commercial Supplies of Products [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Manufacturing commercial supplies of products, revenue recognized	$ 0
AstraZeneca Agreements [Member] \| Measurement Input Discount Rate [Member] \| Discounted Cash Flow [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Discount rate applied	17.5
AstraZeneca Agreements [Member] \| U.S./RoW and China [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-contingent upfront payments received	$ 402,200,000
Variable consideration related to payments for milestones considered probable of being achieved	42,000,000
Variable consideration related to co-development billings	$ 621,600,000

Collaboration Agreements - Summary of Revenue Recognized under Agreement (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	$ 212,958	$ 130,996	$ 183,189
License Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	22,269	9,933	50,607
Development Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	125,913	121,063	132,582
Astellas Agreement [Member] \| License Revenue [Member] \| Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	14,323	0	9,548
Astellas Agreement [Member] \| License Revenue [Member] \| Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	0	0	0
Astellas Agreement [Member] \| Development Revenue [Member] \| Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	2,400	1,588	4,288
Astellas Agreement [Member] \| Development Revenue [Member] \| Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	18,503	18,523	17,487
AstraZeneca Agreements [Member] \| China [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	0	0	0
AstraZeneca Agreements [Member] \| License Revenue [Member] \| U.S./RoW and China [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	7,946	9,933	41,059
AstraZeneca Agreements [Member] \| Development Revenue [Member] \| U.S./RoW and China [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	$ 104,970	$ 100,928	$ 110,677

Collaboration Agreements - Transaction Price Related to Consideration Received and Accounts Receivable Allocated to Performance Obligations along with Associated Deferred Revenue (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Astellas Agreement [Member] \| Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	$ 87,997
Deferred Revenue	286
Total Consideration	88,283
Astellas Agreement [Member] \| Japan [Member] \| License Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	74,089
Deferred Revenue	0
Total Consideration	74,089
Astellas Agreement [Member] \| Japan [Member] \| Development Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	13,908
Deferred Revenue	286
Total Consideration	14,194
Astellas Agreement [Member] \| Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	573,317
Deferred Revenue	3,225
Total Consideration	576,542
Astellas Agreement [Member] \| Europe [Member] \| License Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	370,481
Deferred Revenue	0
Total Consideration	370,481
Astellas Agreement [Member] \| Europe [Member] \| Development Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	202,836
Deferred Revenue	3,225
Total Consideration	206,061
AstraZeneca Agreements [Member] \| U.S./RoW and China [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	702,800
Deferred Revenue	146,369
Total Consideration	849,169
AstraZeneca Agreements [Member] \| U.S./RoW and China [Member] \| License Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	294,163
Deferred Revenue	0
Total Consideration	294,163
AstraZeneca Agreements [Member] \| U.S./RoW and China [Member] \| Co-development, information sharing & committee services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	408,637
Deferred Revenue	20,521
Total Consideration	429,158
AstraZeneca Agreements [Member] \| U.S./RoW and China [Member] \| China performance obligation [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	0
Deferred Revenue	125,848
Total Consideration	$ 125,848

Collaboration Agreements - Summary of Revenue Recognized Under the Collaboration Agreements - Additional Information 4 (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Remainder of transaction price, variable consideration from estimated future co-development billing	$ 1.4
Japan [Member] \| Astellas Agreement [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Changes in revenue due to prior period adjustment of performance obligations	14.9
Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Remainder of transaction price, variable consideration from estimated future co-development billing	14.3
Europe [Member] \| Astellas Agreement [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Changes in revenue due to prior period adjustment of performance obligations	0.6
U.S./RoW and China [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Remainder of transaction price, variable consideration from estimated future co-development billing	197.4
U.S./RoW and China [Member] \| AstraZeneca Agreements [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Changes in revenue due to prior period adjustment of performance obligations	$ 20.2

Collaboration Agreements - Product Revenue - Additional Information 5 (Detail) - Astellas Agreement [Member] - Japan [Member] - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2018
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Contract with customer liability, revenue recognized	$ 43.9	$ 20.9
Product Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Contract with customer liability, revenue recognized			$ 64.8

Fair Value Measurements - Fair Values of Financial Liabilities Carried at Historical Cost (Detail) - Lease financing obligations [Member] - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 98,105	$ 98,476
Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	0	0
Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	0	0
Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 98,105	$ 98,476

Fair Value Measurements - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Transfers of assets from level 1 to 2	$ 0	$ 0	$ 0
Transfers of assets from level 2 to 1	0	0	0
Transfers of liabilities from level 1 to 2	0	0	0
Transfers of liabilities from level 2 to 1	0	0	0
Transfers of assets into level 3	0	0	0
Transfers of assets out of level 3	0	0	0
Transfers of liabilities into level 3	0	0	0
Transfers of liabilities out of level 3	$ 0	$ 0	$ 0

Balance Sheet Components - Schedule of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Cash And Cash Equivalents [Abstract]
Cash	$ 38,783	$ 103,716
US treasury notes and bills	49,934	0
Money market funds	541	569,942
Total cash and cash equivalents	$ 89,258	$ 673,658

Balance Sheet Components - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 192,397	$ 189,117
Less: accumulated depreciation	(65,199)	(59,641)
Property and equipment, net	127,198	129,476
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	101,200	93,758
Building shell [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	53,880	53,879
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	16,405	19,497
Machinery [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	8,382	0
Computer Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,473	6,006
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	5,690	5,575
Construction in progress [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 367	$ 10,402

Balance Sheet Components - Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 587,885	$ 71,360
Gross Unrealized Holding Gains	238	1,252
Gross Unrealized Holding Losses	(159)	(46)
Fair Value	587,964	72,566
US treasury notes and bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	467,296
Gross Unrealized Holding Gains	109
Gross Unrealized Holding Losses	(69)
Fair Value	467,336
Term deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	80,000
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	0
Fair Value	80,000
Certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	30,000
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	(90)
Fair Value	29,910
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		53,985
Gross Unrealized Holding Gains		4
Gross Unrealized Holding Losses		(46)
Fair Value		53,943
Bond and mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,464	17,249
Gross Unrealized Holding Gains	20	1,153
Gross Unrealized Holding Losses	0	0
Fair Value	10,484	18,402
Equity investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	125	126
Gross Unrealized Holding Gains	109	95
Gross Unrealized Holding Losses	0	0
Fair Value	$ 234	$ 221

Balance Sheet Components - Summary of Contractual Maturities Available-for-Sale Investments and Term Deposit (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Investments Schedule [Abstract]
Within one year	$ 532,144
After one year through four years	45,102
Total debt investments	577,246
Bond and mutual funds	10,484
Equity investments	234
Total investments	$ 587,964	$ 72,566

Balance Sheet Components - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Accrued Liabilities Current [Abstract]
Preclinical and clinical trial accruals	$ 35,413	$ 32,321
Payroll and related accruals	21,430	18,810
Property taxes and other	1,095	4,201
Professional services	2,648	1,991
Other	5,537	6,458
Total accrued liabilities	$ 66,123	$ 63,781

Product Development Obligations - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) DevelopmentObligation	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Number of product development obligations \| DevelopmentObligation	11
Accrued product development costs excluding interest	$ 10.8	$ 11.3
Accrued Interest	$ 6.0	$ 5.9
Bank of Finland Interest Rate [Member]
Debt Instrument [Line Items]
Percentage points deducted to reference rate to compute effective interest rate	1.00%
Minimum [Member]
Debt Instrument [Line Items]
Interest rate on product development advances	3.00%

Convertible Note Payable - Additional Information (Detail) - FibroGen China [Member] - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2013	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Convertible promissory note	$ 0.6
Interest rate of convertible promissory note	2.00%
Anniversary date of promissory note		8 years
Other Long Term Liabilities [Member]
Debt Instrument [Line Items]
Total outstanding principal balance and accrued interest		$ 0.7	$ 0.6

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under all Non-Cancelable Operating Lease Obligations (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019	$ 444
2020	232
2021	25
2022	16
2023	0
Total minimum payments	$ 717

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	1 Months Ended		3 Months Ended			12 Months Ended
	Feb. 28, 2013 USD ($) ft²	Sep. 30, 2006 USD ($) ft² $ / ft²	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jun. 30, 2012 USD ($)
Commitments And Contingencies [Line Items]
Restricted time deposits			$ 4,145	$ 5,181		$ 4,145	$ 5,181
FibroGen, Inc. [Member]
Commitments And Contingencies [Line Items]
Land subject to leases \| ft²		234,249
Initial term of lease contract		15 years
Restricted time deposits		$ 7,300
Percentage of letter of credit released					0.125%
Description of lessee leasing arrangements, operating leases						The agreement included an expansion option to occupy part of an adjacent building within 31 months of the lease commencement date of November 20, 2008.
Lease incentive receivable from land lord through expansion option not used									$ 5,000
Percentage of construction costs for tenant improvement		60.00%
Tenant improvement price per square foot of rental space \| $ / ft²		140.50
Tenant improvements allowance of rental space		$ 32,500
Cost of construction capitalized		50,800
Reimbursements from landlord for tenant improvements		$ 32,500
FibroGen, Inc. [Member] \| Reclassified from Restricted Cash to Short-term Investments [Member]
Commitments And Contingencies [Line Items]
Prior period reclassification adjustment			$ 1,000	$ 1,000	$ 1,000
FibroGen China [Member]
Commitments And Contingencies [Line Items]
Land subject to leases \| ft²	4,820
Initial term of lease contract	8 years
Percentage of construction costs for tenant improvement	100.00%
Cost of construction capitalized	$ 3,100
Reimbursements from landlord for tenant improvements	$ 500
Lease starting date	Feb. 01, 2013
Rent expenses for leased facilities						$ 3,100	3,000	$ 2,800
FibroGen China [Member] \| Research and Development Expenses and General and Administrative Expenses [Member]
Commitments And Contingencies [Line Items]
Sublease income received						$ 3,500	$ 3,900	$ 3,800

Commitments and Contingencies - Schedule of Future Minimum Lease Payments on Consolidated Basis Under Company's Facility Financing Lease Obligations (Detail) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments And Contingencies Disclosure [Abstract]
2019	$ 14,379
2020	14,664
2021	14,179
2022	14,335
2023	12,872
Total minimum payments	$ 70,429

Equity and Stock-based Compensation - Subsidiary Stock and Non-Controlling Interests - Additional information (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Nov. 19, 2014
Class Of Stock [Line Items]
Preferred stock, shares outstanding	0	0
IPO [Member]
Class Of Stock [Line Items]
Conversion rights, shares issued upon conversion of each preferred share			958,996
FibroGen Europe [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	42,619,022	42,619,022
Preferred stock redemption percentage	If a Preferred Share can be redeemed by a majority shareholder owning more than ninety percent (90%) of the shares of FibroGen Europe in accordance with the provisions of the Finnish Limited Liability Companies Act, the minority holders of Preferred Shares have the right to request redemption of their shares.
Minimum percentage of shareholder's approval to call for redemption of preferred shares	90.00%
Preferred stock, voting rights	one vote
Conversion rights, shares issued upon conversion of each preferred share	1
FibroGen Europe [Member] \| Series A [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,700,845	1,700,845
FibroGen Europe [Member] \| Series B [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,875,000	1,875,000
FibroGen Europe [Member] \| Series C [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,599,503	1,599,503
FibroGen Europe [Member] \| Series D [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,520,141	1,520,141
FibroGen Europe [Member] \| Series E [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	459,565	459,565
FibroGen Europe [Member] \| Series F [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	5,714,332	5,714,332
FibroGen Europe [Member] \| Series G [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	9,927,500	9,927,500
FibroGen Europe [Member] \| Series H [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	19,822,136	19,822,136
FibroGen China [Member]
Class Of Stock [Line Items]
Conversion rights, shares issued upon conversion of each preferred share	1
FibroGen China [Member] \| Series A [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	6,758,000	6,758,000
Preferred shares issued, price per share	$ 1.00
Cash dividend percentage	6.00%

Equity and Stock-based Compensation - Summary of Common Stock Reserved for Future Issuance (Detail) - shares shares in Thousands	Dec. 31, 2018	Dec. 31, 2017
Class Of Stock [Line Items]
Common stock outstanding	85,432	82,498
Stock options outstanding	10,430	11,550
RSUs outstanding	1,428	1,562
Common stock warrants outstanding	4	4
Shares reserved for future stock options and RSUs grant	6,041	4,190
Total shares of common stock reserved	105,953	101,828
ESPP [Member]
Class Of Stock [Line Items]
Shares reserved for future ESPP offering	2,618	2,024

Equity and Stock-based Compensation - Stock Plans - Additional information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total intrinsic value of options exercised		$ 248,206
RSUs released and issued net of shares withheld for taxes		432,472
Weighted-average fair value of awards granted		$ 53.69	$ 26.59	$ 19.37
2005 Stock Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period of stock options		4 years
2005 Stock Plan \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period of stock options		10 years
2014 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period of stock options		5 years
Expiration period of stock options		10 years
Termination date of equity incentive plan		Nov. 12, 2024
Option vesting term		Option vesting schedules are determined by the Company at the time of issuance and generally have a four year vesting schedule (25% vesting on the first anniversary of the vesting base date and quarterly thereafter over the next 3 years).
Number of common stock reserved for issuance		6,040,725
Common stock reserved for future issuance, Description		Shares reserved for issuance increases on January 1 of each year commencing on January 1, 2016 and ending on January 1, 2024 by the lesser of (i) the amount equal to 4% of the number of shares issued and outstanding on December 31 immediately prior to the date of increase or (ii) such lower number of shares as may be determined by the board of directors. As of December 31, 2018, the Company has reserved 6,040,725 shares of its common stock that remains unissued for issuance under the 2014 Plan.
Percentage of common stock reserved for future issuance	4.00%
Number of common stock repurchased		0	0
Total intrinsic value of options exercised		$ 97,500	$ 111,900	$ 17,900
2014 Equity Incentive Plan \| First Anniversary [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of vesting rights		25.00%
2014 Equity Incentive Plan \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair value exercise price grant date		100.00%

Equity and Stock-based Compensation - Stock Plans - Summary of Stock Option Transactions (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Outstanding, Beginning Balance, Shares \| shares	11,550
Granted, Shares \| shares	1,307
Exercised, Shares \| shares	(2,271)
Expired, Shares \| shares	(7)
Forfeited, Shares \| shares	(149)
Outstanding, Ending Balance, Shares \| shares	10,430
Vested and expected to vest, Shares \| shares	10,430
Exercisable, Shares \| shares	7,644
Outstanding, Beginning Balance, Weighted Average Exercise per Share \| $ / shares	$ 14.82
Granted, Weighted Average Exercise per Share \| $ / shares	53.64
Exercised, Weighted Average Exercise per Share \| $ / shares	11.20
Expired, Weighted Average Exercise per Share \| $ / shares	5.82
Forfeited, Weighted Average Exercise per Share \| $ / shares	30.55
Outstanding, Ending Balance, Weighted Average Exercise per Share \| $ / shares	20.25
Vested and expected to vest, Weighted Average Exercise per Share \| $ / shares	20.25
Exercisable, Weighted Average Exercise per Share \| $ / shares	$ 13.83
Outstanding, Weighted Average Remaining Contractual Life	5 years 5 months 19 days
Vested and expected to vest, Weighted Average Remaining Contractual Life	5 years 5 months 19 days
Exercisable, Weighted Average Remaining Contractual Life	4 years 5 months 19 days
Outstanding, Aggregate Intrinsic Value \| $	$ 281,436
Vested and expected to vest, Aggregate Intrinsic Value \| $	281,436
Exercisable, Aggregate Intrinsic Value \| $	$ 248,206

Equity and Stock-based Compensation - Summary of RSU Activity (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested, Shares, Beginning Balance	1,562
Unvested, Shares, Ending Balance	1,428	1,562
Granted, Fair value at Grant	$ 53.69	$ 26.59	$ 19.37
Restricted Stock Unit [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested, Shares, Beginning Balance	1,562
Granted, Shares	706
Vested, Shares	(727)
Forfeited, Shares	(113)
Unvested, Shares, Ending Balance	1,428	1,562
Unvested, Fair value at Grant, Beginning Balance	$ 24.75
Granted, Fair value at Grant	53.69
Vested, Fair value at Grant	24.70
Forfeited, Fair value at Grant	35.12
Unvested, Fair value at Grant, Ending Balance	$ 38.26	$ 24.75

Equity and Stock-based Compensation - Employee Stock Purchase Plan - Additional information (Detail) - 2014 ESPP [Member] - shares	1 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase of common stock shares at discount	15.00%
Percentage of fair value exercise price grant date	85.00%
Number of common stock reserved for issuance	1,600,000
Common stock reserved for future issuance, Description		The Company has reserved 1,600,000 shares of its common stock for issuance under the 2014 ESPP and shares reserved for issuance increases January 1 of each year commencing January 1, 2016 by the lesser of (i) a number of shares equal to 1% of the total number of outstanding shares of common stock on December 31 immediately prior to the date of increase; (ii) 1,200,000 shares or (iii) such number of shares as may be determined by the board of directors.
Percentage of common stock reserved for future issuance	1.00%
Increase in number of shares of common stock reserved for future issuance, shares	1,200,000
Shares purchased by employees		230,317	250,834	266,720

Equity and Stock-based Compensation - Schedule of Allocated Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 52,142	$ 37,539	$ 32,132
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	30,491	21,807	19,070
General and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 21,651	$ 15,732	$ 13,062

Equity and Stock-based Compensation - Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Employee Stock Purchase Plans (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 4 months 24 days	5 years 8 months 12 days	5 years 3 months 18 days
Expected volatility	67.90%	71.50%	69.90%
Risk-free interest rate	2.70%	2.20%	1.40%
Expected dividend yield	0.00%	0.00%	0.00%
Weighted average estimated fair value	$ 32.12	$ 16.96	$ 11.49
Employee stock purchase plans [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	47.30%	52.80%	61.90%
Expected volatility, maximum	75.30%	77.20%	80.70%
Risk-free interest rate, minimum	0.80%	0.50%	0.20%
Risk-free interest rate, maximum	2.90%	1.60%	1.00%
Expected dividend yield	0.00%	0.00%	0.00%
Weighted average estimated fair value	$ 16.27	$ 9.41	$ 9.94
Employee stock purchase plans [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months	6 months	6 months
Employee stock purchase plans [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	2 years	2 years	2 years

Equity and Stock-based Compensation - Stock-Based Compensation - Additional information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Stock Option Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs	$ 46.6
Non-vested stock option awards granted that will be recognized on a straight-line basis over the weighted-average period	2 years 2 months 26 days
Restricted Stock Unit [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested stock option awards granted that will be recognized on a straight-line basis over the weighted-average period	2 years 4 months 24 days
Unrecognized compensation costs	$ 40.9

Equity and Stock-based Compensation - Schedule of Warrants to Purchase Shares of Common Stock (Detail)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Class Of Warrant Or Right [Line Items]
Number of Shares	4,430
Year of Issuance 2000 [Member]
Class Of Warrant Or Right [Line Items]
Year of Issuance	2000
Number of Shares	4,430
Exercise Price per Share \| $ / shares	$ 15.00
Reason for Issuance	Issued in connection with lease agreement
Expiration Date	Five years after initial public offering or upon merger or sale of the Company’s assets, whichever occurs first

Net Loss Per Share - Schedule of Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	11,862	13,116	14,875
Employee stock options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	10,430	11,550	13,660
RSUs outstanding [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	1,428	1,562	1,211
Warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	4	4	4

Income Taxes - Components of Loss Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Components Of Income Tax Expense Benefit Continuing Operations [Abstract]
Domestic	$ (38,472)	$ (80,735)	$ (25,342)
Foreign	(47,644)	(39,819)	(32,797)
Loss before income taxes	$ (86,116)	$ (120,554)	$ (58,139)

Income Taxes - Schedule of Components of Provision For (Benefit From) Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ 0	$ 0	$ 0
State	2	2	2
Foreign	302	319	139
Total current	304	321	141
Deferred:
Federal	0	0	(212)
State	0	0	0
Foreign	0	0	0
Total deferred	0	0	(212)
Total provision for (benefit from) income taxes	$ 304	$ 321	$ (71)

Income Taxes - Schedule of Reconciliation Between Statutory Federal Income Tax Rate and Effective Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Tax at statutory federal rate	21.00%	34.00%	34.00%
State tax	0.00%	0.00%	0.00%
Stock-based compensation expense	14.50%	18.50%	(7.90%)
Change in deferred tax assets due to rate change	0.00%	43.90%	0.00%
Change in valuation allowance due to rate change	0.00%	(43.90%)	0.00%
Net operating losses not benefitted	(23.20%)	(43.80%)	(12.90%)
Foreign net operating losses not benefitted	(11.60%)	(6.70%)	(13.00%)
Orphan drug credit	0.00%	(2.00%)	0.00%
Other	(1.10%)	(0.30%)	(0.10%)
Total	(0.40%)	(0.30%)	0.10%

Income Taxes - Schedule of Significant Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Components Of Deferred Tax Assets And Liabilities [Abstract]
Federal and state net operating loss carryforwards	$ 91,683	$ 71,256
Tax credit carryforwards	45,885	39,488
Foreign net operating loss carryforwards	21,295	15,052
Stock-based compensation	9,281	7,835
Lease obligations	2,511	2,737
Reserves and accruals	6,072	4,851
Deferred revenue	16,454	18,103
Fixed assets	356	0
Other	450	420
Subtotal	193,987	159,742
Less: Valuation allowance	(193,987)	(159,540)
Net deferred tax assets	0	202
Fixed assets	0	(181)
Other	0	(21)
Net deferred tax liabilities	0	(202)
Total net deferred tax assets	$ 0	$ 0

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes [Line Items]
Increase in valuation allowance	$ 34,400,000	$ 30,500,000	$ 12,300,000
Federal and state net operating loss carryforwards	91,683,000	71,256,000
Foreign net operating loss carryforwards	$ 21,295,000	$ 15,052,000
Tax at statutory federal rate	21.00%	34.00%	34.00%
Percentage of ownership changes	0.00%
Unrecognized tax benefits	$ 28,000,000
Unrecognized tax benefits that would affect effective tax rate	500,000
Accrued interest, unrecognized tax benefits	$ 0		$ 0
Unrecognized tax benefits description	The Company does not anticipate a material change to its unrecognized tax benefits over the next twelve months that would affect the Company’s effective tax rate.
Earliest Tax Year [Member]
Income Taxes [Line Items]
Foreign statute of limitation generally remains open in the year	2009
Latest Tax Year [Member]
Income Taxes [Line Items]
Foreign statute of limitation generally remains open in the year	2018
ASU 2016-09 [Member]
Income Taxes [Line Items]
Increase in valuation allowance	$ 19,500,000
Retrospective increase in deferred tax assets for previously unrecognized excess tax benefits	19,500,000
Maximum [Member]
Income Taxes [Line Items]
Tax at statutory federal rate		35.00%
Foreign net operating loss [Member]
Income Taxes [Line Items]
Foreign net operating loss carryforwards	$ 86,300,000
Foreign net operating loss [Member] \| Minimum [Member]
Income Taxes [Line Items]
Operating loss carryforwards expiration year	2019
Foreign net operating loss [Member] \| Maximum [Member]
Income Taxes [Line Items]
Operating loss carryforwards expiration year	2028
Federal [Member]
Income Taxes [Line Items]
Federal and state net operating loss carryforwards	$ 400,300,000
Operating loss carryforwards expiration year	2026
Other tax credit carryforwards	$ 46,400,000
Other tax credit carryforwards expiration year	2019
State [Member]
Income Taxes [Line Items]
Federal and state net operating loss carryforwards	$ 148,100,000
Operating loss carryforwards expiration year	2019
State [Member] \| California [Member]
Income Taxes [Line Items]
Other tax credit carryforwards	$ 26,300,000

Income Taxes - Reconciliation of the Beginning and Ending Amounts of Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Ending Balance	$ 28,000
Federal and State [Member]
Income Tax Contingency [Line Items]
Beginning balance	23,361	$ 19,654	$ 24,213
Decrease due to prior positions		(2,044)	(7,109)
Increase due to current year position	4,216	5,448	2,550
Increase due to prior positions	379	303
Ending Balance	$ 27,956	$ 23,361	$ 19,654

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Accounts receivable from related party	$ 47,210	$ 4,004
Accrued liabilities to related party	444	272
Astellas [Member] \| Collaborative Arrangement [Member]
Related Party Transaction [Line Items]
Revenue related to collaboration agreements	100,000	20,100	$ 31,300
Expense related to collaboration agreements	1,500	1,000	$ 6,400
Accounts receivable from related party	47,200	4,000
Accrued liabilities to related party	400	$ 300
API Shipment [Member] \| Astellas [Member] \| Astellas Agreement [Member]
Related Party Transaction [Line Items]
Accrued liabilities to related party	43,800
Product Revenue [Member] \| API Shipment [Member] \| Astellas [Member]
Related Party Transaction [Line Items]
Revenue related to collaboration agreements	$ 64,800

Segment and Geographic Information - Schedule of Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenue recognized	$ 212,958	$ 130,996	$ 183,189
Europe [Member]
Segment Reporting Information [Line Items]
Revenue recognized	112,916	110,861	151,736
Japan [Member] \| Related Party [Member]
Segment Reporting Information [Line Items]
Revenue recognized	100,002	20,111	31,323
All other [Member]
Segment Reporting Information [Line Items]
Revenue recognized	$ 40	$ 24	$ 130

Segment and Geographic Information - Schedule of Long Lived Assets by Geographic Area (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Revenues From External Customers And Long Lived Assets [Line Items]
Property and equipment, net	$ 127,198	$ 129,476
United States [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Property and equipment, net	103,539	107,228
China [Member]
Revenues From External Customers And Long Lived Assets [Line Items]
Property and equipment, net	$ 23,659	$ 22,248

Segment and Geographic Information - Schedule of Customer Concentration by Collaboration Partners (Detail) - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Percentage of Revenue [Member] \| Astellas-Related party [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk, percentage	47.00%	15.00%	17.00%
Percentage of Revenue [Member] \| AstraZeneca [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk, percentage	53.00%	85.00%	83.00%
Percentage of Accounts Receivable [Member] \| Astellas-Related party [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk, percentage	74.00%	47.00%
Percentage of Accounts Receivable [Member] \| AstraZeneca [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk, percentage	26.00%	53.00%

Schedule II - Valuation and Qualifying Accounts (Detail) - Valuation Allowances for Deferred Tax Assets [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 159,540	$ 128,995	$ 116,718
Charged (Credited) to Statement of Operation	34,447	11,039	12,277
Charged to Other Accounts - Equity	0	19,506	0
Deductions, Net	0	0	0
Balance at End of Year	$ 193,987	$ 159,540	$ 128,995

FibroGen, Inc. 401(k) Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Defined contribution plan, maximum annual contributions per employee, percent	60.00%
Defined contribution plan, employer matching contributions	$ 2.9	$ 2.5	$ 2.3

Equity and Stock-based Compensation - Common Stock - Additional information (Detail)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Common stock voting rights	one vote

Segment and Geographic Information - Additional information (Detail)	12 Months Ended
	Dec. 31, 2018 Segment
Segment Reporting [Abstract]
Number of operating segment	1