FibroGen (FGEN) 10-Q 8 Aug 19 2019 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2019	Jul. 31, 2019
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q2
Trading Symbol	FGEN
Entity Registrant Name	FIBROGEN INC
Entity Central Index Key	0000921299
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Title of 12(b) Security	Common Stock, $0.01 par value
Security Exchange Name	NASDAQ
Entity File Number	1-36740
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0357827
Entity Address, Address Line One	409 Illinois Street
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94158
City Area Code	415
Local Phone Number	978-1200
Document Quarterly Report	true
Document Transition Report	false
Entity Common Stock Shares Outstanding		86,915,996

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 74,587	$ 89,258
Short-term investments	586,174	532,144
Accounts receivable ($4,311 and $47,210 from a related party)	6,453	63,684
Inventories	1,981	0
Prepaid expenses and other current assets ($127,981 and $0 from a related party)	136,596	4,929
Total current assets	805,791	690,015
Restricted time deposits	4,145	4,145
Long-term investments	10,915	55,820
Property and equipment, net	44,865	127,198
Finance lease right-of-use assets	44,536	0
Other assets	4,814	3,420
Total assets	915,066	880,598
Current liabilities:
Accounts payable	4,060	9,139
Accrued and other current liabilities ($781 and $444 to a related party)	66,545	66,123
Deferred revenue	136	13,771
Finance lease liabilities, current	12,071	0
Total current liabilities	82,812	89,033
Long-term portion of lease obligations	1,342	97,157
Product development obligations	16,846	16,798
Deferred rent	0	3,038
Deferred revenue, net of current	102,926	136,109
Finance lease liabilities, non-current	43,780	0
Other long-term liabilities	19,058	9,993
Total liabilities	266,764	352,128
Commitments and Contingencies
Stockholders’ equity:
Preferred stock, $0.01 par value; 125,000 shares authorized; no shares issued and outstanding at June 30, 2019 and December 31, 2018	0	0
Common stock, $0.01 par value; 225,000 shares authorized at June 30, 2019 and December 31, 2018; 86,847 and 85,432 shares issued and outstanding at June 30, 2019 and December 31, 2018	868	854
Additional paid-in capital	1,265,783	1,226,453
Accumulated other comprehensive loss	(462)	(2,281)
Accumulated deficit	(637,158)	(715,827)
Total stockholders’ equity	629,031	509,199
Non-controlling interests	19,271	19,271
Total equity	648,302	528,470
Total liabilities, stockholders’ equity and non-controlling interests	$ 915,066	$ 880,598

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Accounts receivable from related party	$ 4,311,000	$ 47,210,000
Prepaid expenses and other current assets from related party	127,981,000	0
Accrued and other current liabilities to related party	$ 781,000	$ 444,000
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	86,847,000	85,432,000
Common stock, shares outstanding	86,847,000	85,432,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue:
Total revenue	$ 191,566	$ 43,952	$ 215,429	$ 75,876
Operating expenses:
Research and development	52,008	52,138	102,505	109,112
Selling, general and administrative	26,739	15,055	48,948	30,605
Total operating expenses	78,747	67,193	151,453	139,717
Income (loss) from operations	112,819	(23,241)	63,976	(63,841)
Interest and other, net
Interest expense	(736)	(2,750)	(1,507)	(5,519)
Interest income and other, net	4,125	2,645	8,303	4,717
Total interest and other, net	3,389	(105)	6,796	(802)
Income (loss) before income taxes	116,208	(23,346)	70,772	(64,643)
Provision for income taxes	205	75	180	174
Net income (loss)	$ 116,003	$ (23,421)	$ 70,592	$ (64,817)
Net income (loss) per share:
Basic	$ 1.34	$ (0.28)	$ 0.82	$ (0.78)
Diluted	$ 1.26	$ (0.28)	$ 0.77	$ (0.78)
Weighted average number of common shares used to calculate net income (loss) per share:
Basic	86,445	83,750	86,077	83,309
Diluted	91,728	83,750	92,069	83,309
License Revenue [Member]
Revenue:
Total revenue	$ 150,581	$ 14,323	$ 150,581	$ 14,323
Development and Other Revenue [Member]
Revenue:
Total revenue	$ 40,985	$ 29,629	$ 64,848	$ 61,553

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Operations (Unaudited) (Parenthetical) - Astellas Agreement [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Collaboration services and other revenue from a related party	$ 17,223	$ 6,145	$ 22,082	$ 11,317
License and milestone revenue from a related party	$ 117,470	$ 14,323	$ 117,470	$ 14,323

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 116,003	$ (23,421)	$ 70,592	$ (64,817)
Other comprehensive income (loss):
Foreign currency translation adjustments	(180)	958	111	431
Available-for-sale investments:
Unrealized gain on investments, net of tax effect	655	53	1,097	3
Other comprehensive income, net of taxes	475	1,011	1,208	434
Comprehensive income (loss)	$ 116,478	$ (22,410)	$ 71,800	$ (64,383)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - 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, 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 in accounting principle upon adoption | ASU 2016-01 [Member]	0	$ 0	0	(1,250)	1,250	0
Net income (loss)	(64,817)	0	0	0	(64,817)	0
Change in unrealized gain or loss on investments	3	0	0	3	0	0
Foreign currency translation adjustments	431	0	0	431	0	0
Shares issued from stock plans, net of payroll taxes paid	7,338	$ 17	7,321	0	0	0
Shares issued from stock plans, net of payroll taxes paid, Shares		1,684,716
Stock-based compensation	24,109	$ 0	24,109	0	0	0
Balance at Jun. 30, 2018	514,802	$ 842	1,191,524	(2,611)	(694,224)	19,271
Balance, Shares at Jun. 30, 2018		84,182,844
Balance at Mar. 31, 2018	518,789	$ 834	1,173,109	(3,622)	(670,803)	19,271
Balance, Shares at Mar. 31, 2018		83,420,625
Net income (loss)	(23,421)	$ 0	0	0	(23,421)	0
Change in unrealized gain or loss on investments	53	0	0	53	0	0
Foreign currency translation adjustments	958	0	0	958	0	0
Shares issued from stock plans, net of payroll taxes paid	5,192	$ 8	5,184	0	0	0
Shares issued from stock plans, net of payroll taxes paid, Shares		762,219
Stock-based compensation	13,231	$ 0	13,231	0	0	0
Balance at Jun. 30, 2018	514,802	$ 842	1,191,524	(2,611)	(694,224)	19,271
Balance, Shares at Jun. 30, 2018		84,182,844
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
Impact of change in accounting principle upon adoption | ASU 2016-02 [Member]	8,688	$ 0	0	0	8,688	0
Impact of change in accounting principle upon adoption | ASU 2018-02 [Member]	0	0	0	611	(611)	0
Net income (loss)	70,592	0	0	0	70,592	0
Change in unrealized gain or loss on investments	1,097	0	0	1,097	0	0
Foreign currency translation adjustments	111	0	0	111	0	0
Shares issued from stock plans, net of payroll taxes paid	5,272	$ 14	5,258	0	0	0
Shares issued from stock plans, net of payroll taxes paid, Shares		1,414,970
Stock-based compensation	34,072	$ 0	34,072	0	0	0
Balance at Jun. 30, 2019	648,302	$ 868	1,265,783	(462)	(637,158)	19,271
Balance, Shares at Jun. 30, 2019		86,847,072
Balance at Mar. 31, 2019	508,494	$ 861	1,242,460	(937)	(753,161)	19,271
Balance, Shares at Mar. 31, 2019		86,129,564
Net income (loss)	116,003	$ 0	0	0	116,003	0
Change in unrealized gain or loss on investments	655	0	0	655	0	0
Foreign currency translation adjustments	(180)	0	0	(180)	0	0
Shares issued from stock plans, net of payroll taxes paid	5,688	$ 7	5,681	0	0	0
Shares issued from stock plans, net of payroll taxes paid, Shares		717,508
Stock-based compensation	17,642	$ 0	17,642	0	0	0
Balance at Jun. 30, 2019	$ 648,302	$ 868	$ 1,265,783	$ (462)	$ (637,158)	$ 19,271
Balance, Shares at Jun. 30, 2019		86,847,072

Condensed Consolidated Statem_5

Condensed Consolidated Statement of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Operating activities
Net income (loss)	$ 70,592	$ (64,817)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation	5,523	3,083
Amortization of finance lease right-of-use assets	5,140	0
Net amortization of premium and discount on investments	(2,457)	463
Unrealized loss (gain) on cash equivalents and short-term equity investments	(59)	1,127
Loss (gain) on disposal of property and equipment	(10)	53
Stock-based compensation	34,072	24,109
Realized foreign currency gain	0	(1,074)
Realized gain on sales of available-for-sale securities	0	(87)
Changes in operating assets and liabilities:
Accounts receivable	57,231	(21,737)
Inventories	(1,981)	0
Prepaid expenses and other current assets	(131,803)	(13,197)
Other assets	(200)	(722)
Accounts payable	(5,079)	(2,287)
Accrued and other liabilities	917	(13,371)
Deferred revenue	(46,818)	20,370
Lease obligations	0	25
Accrued interest for finance lease liabilities	241	0
Other long-term liabilities	8,519	1,135
Net cash used in operating activities	(6,172)	(66,927)
Investing activities
Purchases of property and equipment	(2,206)	(3,705)
Proceeds from sale of property and equipment	0	184
Purchases of available-for-sale securities and term deposit	(105,511)	(98)
Proceeds from sales of available-for-sale securities	0	8,167
Proceeds from maturities of investments	100,000	25,390
Net cash provided by (used in) investing activities	(7,717)	29,938
Financing activities
Repayments of finance lease liabilities	(5,850)	0
Repayments of lease obligations	(202)	(201)
Cash paid for payroll taxes on restricted stock unit releases	(8,065)	(10,005)
Proceeds from issuance of common stock	13,337	17,343
Net cash provided by (used in) financing activities	(780)	7,137
Effect of exchange rate change on cash and cash equivalents	(2)	(3)
Net decrease in cash and cash equivalents	(14,671)	(29,855)
Total cash and cash equivalents at beginning of period	89,258	673,658
Total cash and cash equivalents at end of period	$ 74,587	$ 643,803

Significant Accounting Policies

Significant Accounting Policies	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Significant Accounting Policies	1. Significant Accounting Policies Description of Operations FibroGen, Inc. (“FibroGen” or the “Company”), incorporated in 1993 in Delaware and headquartered in San Francisco, California, with subsidiary offices in Beijing and Shanghai, People’s Republic of China (“China”), is a leading biopharmaceutical company discovering and developing a pipeline of first-in-class therapeutics. The Company applies its pioneering expertise in hypoxia-inducible factor (“HIF”), connective tissue growth factor (“CTGF”) biology, and clinical development to advance innovative medicines for the treatment of anemia, fibrotic disease, and cancer. Roxadustat, the Company’s most advanced product candidate, is an oral small molecule inhibitor of HIF prolyl hydroxylase (“HIF-PH”) activity, completing Phase 3 clinical development worldwide for the treatment of anemia in chronic kidney disease (“CKD”), with a New Drug Application (“NDA”) now approved by the National Medical Products Administration (“NMPA”) in China. The Company and its collaboration partners AstraZeneca AB (“AstraZeneca”) and Astellas Pharma Inc. (“Astellas”) are in the process of preparing an NDA for submission to the United States (“U.S.”) Food and Drug Administration (“FDA”) and a Marketing Authorization Application (“MAA”) for submission to the European Medicines Agency (“EMA”) this year. Astellas submitted an NDA for the treatment of anemia in CKD patients on dialysis in Japan in September 2018, which is currently under review by the Pharmaceuticals and Medical Devices Agency (“PMDA”). Roxadustat is in Phase 3 clinical development in the U.S. and Europe and in Phase 2/3 development in China for anemia associated with myelodysplastic syndromes (“MDS”). Pamrevlumab, an anti-CTGF human monoclonal antibody, is in Phase 3 clinical development for the treatment of idiopathic pulmonary fibrosis (“IPF”), and advancing towards Phase 3 for the treatment of pancreatic cancer. Pamrevlumab is also currently in a Phase 2 trial for Duchenne muscular dystrophy (“DMD”). FibroGen is also developing a biosynthetic cornea in China. Basis of Presentation and Principles of Consolidation The condensed consolidated financial statements include the accounts of FibroGen, its wholly owned subsidiaries and its majority-owned subsidiaries, FibroGen Europe Oy 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. The unaudited condensed consolidated financial statements and related disclosures have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) applicable to interim financial reporting and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X of the U.S. Securities and Exchange Commission (“SEC”) and, therefore, do not include all information and footnote disclosures normally included in the annual consolidated financial statements. The financial information included herein should be read in conjunction with the consolidated financial statements and related notes in the Company’s Annual Report on Form 10-K filed with the SEC for the year ended December 31, 2018 (“2018 Form 10-K”). The accounting policies used by the Company in its presentation of interim financial results are consistent with those presented in Note 2 to the consolidated financial statements included in the 2018 Form 10-K, except for the following: Leases The Company determines if an arrangement is a lease at inception date when it is given control of the underlying assets. The Company elected the practical expedient not to apply the lease recognition and measurement requirements to short-term leases, which is any lease with a term of 12 months or less as of the commencement date that does not include an option to purchase the underlying asset that the lessee is reasonably certain to exercise. The Company’s building leases previously accounted for as build-to-suit arrangements prior to the adoption of Accounting Standards Codification (“ASC”) 842 - Leases Lease right-of-use (“ROU”) assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. As its leases do not typically provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. The Company will reassess the incremental borrowing rate periodically for application to any new leases or lease modifications or if any company-specific or general business conditions warrant. Lease ROU assets include any lease payments made and initial direct costs incurred. The Company has lease agreements with lease and non-lease components. The Company generally accounts for each lease component separately from the non-lease components, and excludes all non-lease components from the calculation of minimum lease payments in measuring the ROU asset and lease liability . The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease terms. Regarding leases denominated in a foreign currency, the related ROU assets and the corresponding ROU asset amortization costs are remeasured using the exchange rate in effect at the date of initial recognition; the related lease liabilities are remeasured using the exchange rate in effect at the end of the reporting period; the lease costs and interest expenses related to lease liability accretion are remeasured using average exchange rates for the reporting period. Finance leases are included in finance lease ROU assets, finance lease liabilities, current and non-current on the Company’s consolidated balance sheets. Operating leases are included in other assets, accrued and other current liabilities, and other long-term liabilities on the Company’s consolidated balance sheets. Inventories Inventories are stated at the lower of cost and net realizable value. The cost of inventories are determined using full absorption and standard costing, which approximates cost based on a first-in, first-out method. The Company reviews the standard costs of raw materials, work-in-process and finished goods periodically, and at least annually, to ensure that its inventories approximate current actual costs. The cost of inventories includes direct material costs, direct labor and manufacturing overhead. The Company regularly reviews the need to adjust the carrying value of excess and obsolete inventories to their estimated net realizable value, if less than cost, based primarily on its estimated forecast of product demand and product expiration period. 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 and deferred 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. In the Company’s opinion, the accompanying unaudited condensed consolidated financial statements include all normal recurring adjustments necessary for a fair statement of its financial position, results of operations and cash flows for the interim periods presented. Net Income (Loss) per Share The following is a reconciliation of the basic and diluted net income (loss) per share calculation for the periods presented (in thousands, except per share data): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Net income (loss) $ 116,003 $ (23,421 ) $ 70,592 $ (64,817 ) Weighted average shares used to compute net income (loss) per share: Basic 86,445 83,750 86,077 83,309 Dilutive effect of potential common shares 5,283 — 5,992 — Diluted 91,728 83,750 92,069 83,309 Net income (loss) per share: Basic $ 1.34 $ (0.28 ) $ 0.82 $ (0.78 ) Diluted $ 1.26 $ (0.28 ) $ 0.77 $ (0.78 ) Diluted shares did not include 4.4 million and 3.4 million securities for the three and six months ended June 30, 2019, and 8.8 million and 8.7 million securities for the three and six months ended June 30, 2018, respectively, as they were anti-dilutive. Recently Issued and Adopted Accounting Guidance ASC 842 In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842) Leases (Topic 842): Targeted Improvements The Company adopted the above guidance under ASC 842 as of January 1, 2019, using the modified retrospective transition method, through a cumulative-effect adjustment at the beginning of the first quarter of 2019. The Company elected the optional transition method under the guidance, which allowed it to continue applying previous lease guidance (ASC 840) for the comparative prior year periods presentation in the year of adoption. Accordingly, the Company recognized a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. In addition, the Company elected the package of transitional practical expedients permitted under the transition guidance under ASC 842, which among other things allows the Company to carry forward its historical lease classification, and not to reassess initial direct costs for any existing leases. Meanwhile, the Company did not elect the hindsight practical expedient because it has limited number of leases, lease terms are straightforward, and most of its lease renewals are undefined until negotiated. In addition, the Company has elected the short term accounting policy practical expedient and does not apply the balance sheet recognition requirements for short-term leases (excluding expenses relating to leases with a lease term of one month or less), by class of underlying asset to which the right of use relates. The Company has not elected the non-lease components practical expedient, and therefore accounts for each lease component separately from the non-lease components. Upon adoption of ASC 842, the Company classified its existing building leases that were previously accounted for as build-to-suit arrangements as finance leases, and applied the transition guidance. Accordingly, the Company derecognized the assets and liabilities previously recognized under ASC 840 build-to-suit guidance. In addition, as a result of applying the transition guidance, the Company also recorded an adjustment to the accumulated depreciation of related leasehold improvements to reflect a change in estimated useful life from the building life to the shorter of the building life and remaining lease term. Differences between the assets and liabilities derecognized were recorded to the opening balance of retained earnings. The impacts to the select line items from the Company’s condensed consolidated balance sheet upon adoption of the ASC 842 guidance are as follows (in thousands): Balance Sheet Line Item Nature of Adjustment New Lease Guidance Adoption Adjustment Assets Property and equipment, net Derecognition - build-to-suit lease assets - building shell, cost $ (53,880 ) Derecognition - build-to-suit lease assets - building shell, accumulated depreciation 13,476 Change of useful life - leasehold improvements, accumulated depreciation (38,877 ) Finance lease right-of-use assets Recognition - finance lease ROU assets 49,597 Other assets Recognition - operating lease ROU assets 730 Liabilities Accrued and other current liabilities Derecognition - deferred rent, current (619 ) Derecognition - build-to-suit lease liabilities, current (545 ) Recognition - operating lease liabilities, current 404 Finance lease liabilities, current Recognition - finance lease liabilities, current 11,499 Long-term portion of lease obligations Derecognition - build-to-suit lease liabilities, non-current (95,613 ) Deferred rent Derecognition - deferred rent, non-current (3,038 ) Finance lease liabilities, non-current Recognition - finance lease liabilities, non-current 49,884 Other long-term liabilities Recognition - operating lease liabilities, non-current 250 Stockholders’ equity Accumulated deficit Cumulative decrease to accumulated deficit $ 8,688 The adoption of this guidance did not have a material impact to the Company’s condensed consolidated statement of operations or condensed consolidated statement of cash flows for the six months ended June 30, 2019. ASU 2018-02 In February 2018, the FASB issued ASU 2018-02, Income Statement - Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income Accumulated Other Comprehensive Loss Accumulated Deficit Balance at December 31, 2018 $ (2,281 ) $ (715,827 ) Impact of change in accounting principle upon adoption of ASU 2018-02 611 (611 ) Opening balance as of January 1, 2019 $ (1,670 ) $ (716,438 ) The adoption of this guidance had no impact to the Company’s condensed consolidated statement of operations or condensed consolidated statement of cash flows for the six months ended June 30, 2019. SEC Disclosure Requirement In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, “Disclosure Update and Simplification,” ASU 2018-07 In June 2018, the FASB issued ASU 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting. 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. 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. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments Financial Instruments – Credit Losses (Topic 326): Targeted Transition Relief

Collaboration Agreements

Collaboration Agreements	6 Months Ended
	Jun. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration Agreements	2. Collaboration Agreements Astellas Agreements Japan Agreement In June 2005, the Company entered into a collaboration agreement with 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). Under the Japan Agreement, the Company is also eligible to receive from Astellas an aggregate of approximately $132.5 million in potential milestone payments, comprised of (i) up to $22.5 million in milestone payments upon achievement of specified clinical and development milestone events (such amounts were fully received as of July 2016), (ii) up to $95.0 million in milestone payments upon achievement of specified regulatory milestone events, and (iii) up to approximately $15.0 million in milestone payments upon the achievement of specified commercial sales milestone. The aggregate amount of such consideration received through June 30, 2019 totals $77.6 million. 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). Under the Europe Agreement, the Company is also eligible to receive from Astellas an aggregate of approximately $425.0 million in potential milestone payments, comprised of (i) up to $90.0 million in milestone payments upon achievement of specified clinical and development milestone events (such amounts were fully received as of 2012), (ii) up to $335.0 million in milestone payments upon achievement of specified regulatory milestone events. 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. The aggregate amount of such consideration received through June 30, 2019 totals $410.0 million. 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 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 AstraZeneca and Astellas. 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. During the second quarter of 2019, the Company received positive topline results from analyses of pooled major adverse cardiac event (“MACE”) and MACE+ data from its Phase 3 trials evaluating roxadustat as a treatment for dialysis and non-dialysis CKD patients, enabling Astellas to prepare for an MAA submission to the EMA during their fiscal year 2019, which ends on March 31, 2020, following the Company’s NDA submission to the FDA. The Company evaluated the two regulatory milestone payments associated with the planned MAA submission and concluded that these milestones became probable of being achieved in the second quarter of 2019. Accordingly, the total consideration of $130.0 million associated with these milestones was included in the transaction price and allocated to performance obligations under the Europe Agreement in the second quarter of 2019, of which $129.5 million was recognized as revenue during the period from performance obligations satisfied or partially satisfied as of June 30, 2019. According to the Europe Agreement, these milestone payments are not billable to Astellas until the submission of an MAA, therefore this $130.0 million was recorded as an unbilled contract asset as of June 30, 2019. AstraZeneca Agreements U.S./Rest of World (“RoW”) 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 paid upfront, non-contingent, non-refundable and time-based payments totaling $374.0 million (such amounts were fully received as of June 2016). Under the U.S./RoW Agreement, the Company is also eligible to receive from AstraZeneca an aggregate of approximately $875.0 million in potential milestone payments, comprised of (i) up to $65.0 million in milestone payments upon achievement of specified clinical and development milestone events, $15.0 million of which was received in 2015 as a result of the finalization of its two audited pre-clinical carcinogenicity study reports, (ii) up to $325.0 million in milestone payments upon achievement of specified regulatory milestone events, (iii) up to $160.0 million in milestone payments related to activity by potential competitors and (iv) up to approximately $325.0 million in milestone payments upon the achievement of specified commercial sales events. The aggregate amount of such consideration received through June 30, 2019 totals $389.0 million. As mentioned above, during the second quarter of 2019, the Company received positive topline results from analyses of pooled MACE and MACE+ data from its Phase 3 trials for roxadustat, enabling the Company’s NDA submission to the FDA. The Company evaluated the regulatory milestone payment associated with this planned NDA submission and concluded that this milestone became probable of being achieved in the second quarter of 2019. Accordingly, the consideration of $50.0 million associated with this milestone was included in the transaction price and allocated to performance obligations under the U.S./ RoW Agreement in the second quarter of 2019, of which $41.6 million was recognized as revenue during the period from performance obligations satisfied or partially satisfied as of June 30, 2019. According to the U.S/RoW Agreement, this milestone payment is not billable to AstraZeneca until the Company has submitted the NDA, therefore this $50.0 million was recorded as an unbilled contract asset as of June 30, 2019. 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 paid upfront, non-contingent and non-refundable payments totaling $28.2 million (such amounts were fully received in 2014). Under the China Agreement, the Company is also eligible to receive from AstraZeneca an aggregate of approximately $348.5 million in potential milestone payments, comprised of (i) up to $15.0 million in milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $146.0 million in milestone payments upon achievement of specified regulatory milestone events, and (iii) up to approximately $187.5 million in milestone payments upon the achievement of specified commercial sales and other events. 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. The aggregate amount of such consideration received through June 30, 2019 totals $55.2 million. 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 AstraZeneca and Astellas. 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. On December 17, 2018, FibroGen (China) Medical Technology Development Co., Ltd. (“FibroGen Beijing”), received marketing authorization from the NMPA for roxadustat, a first-in-class HIF-PH 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 Beijing 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. These milestones payments were received in the first quarter of 2019. Summary of Revenue Recognized Under the Collaborati on 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 condensed consolidated statements of operations. All other elements identified below are included in the “Development and other revenue” line item in the condensed consolidated statements of operations. Amounts recognized as revenue under the Japan Agreement were as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, Agreement Performance Obligation 2019 2018 2019 2018 Japan License revenue $ — $ 14,323 $ — $ 14,323 Development revenue $ 369 $ 1,142 $ 615 $ 1,591 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 June 30, 2019 Deferred Revenue at June 30, 2019 Total Consideration Through June 30, 2019 License $ 74,089 $ — $ 74,089 Development revenue 14,523 136 14,659 Total license and development revenue $ 88,612 $ 136 $ 88,748 The revenue recognized under the Japan Agreement for the three months ended June 30, 2019 included an immaterial amount resulting from changes to estimated variable consideration in the current period relating to performance obligations satisfied or partially satisfied in previous periods. The remainder of the transaction price related to the Japan Agreement includes $0.5 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): Three Months Ended June 30, Six Months Ended June 30, Agreement Performance Obligation 2019 2018 2019 2018 Europe License revenue $ 117,470 $ — $ 117,470 $ — Development revenue $ 16,854 $ 5,003 $ 21,467 $ 9,726 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 June 30, 2019 Deferred Revenue at June 30, 2019 Total Consideration Through June 30, 2019 License $ 487,951 $ — $ 487,951 Development revenue 224,304 2,019 226,323 Total license and development revenue $ 712,255 $ 2,019 * $ 714,274 _______________________________________________________________________________________________________ * Contract assets and liabilities related to rights and obligations in the same contract are recorded net on the condensed consolidated balance sheets. As of June 30, 2019, prepaid expenses and other current assets included a net unbilled contract asset of $128.0 million related to the Europe Agreement, which represents the net of the above-mentioned unbilled contract asset of $130.0 million, and $2.0 million of deferred revenue presented above. The revenue recognized under the Europe Agreement for the three months ended June 30, 2019 included an increase in revenue of $129.2 million resulting from changes to estimated variable consideration in the current period relating to performance obligations satisfied or partially satisfied in previous periods. The remainder of the transaction price related to the Europe Agreement includes $9.4 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 U.S./RoW Agreement were as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, Agreement Performance Obligation 2019 2018 2019 2018 U.S. / RoW and China License revenue $ 33,111 $ — $ 33,111 $ — Development revenue 23,762 23,479 42,766 50,202 China performance obligation $ — $ — $ — $ — 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 June 30, 2019 Deferred Revenue at June 30, 2019 Total Consideration Through June 30, 2019 License $ 327,275 $ — $ 327,275 Co-development, information sharing & committee services 451,402 16,342 467,744 China performance obligation — 136,584 136,584 Total license and development revenue $ 778,677 $ 152,926 * $ 931,603 _______________________________________________________________________________________________________ * Contract assets and liabilities related to rights and obligations in the same contract are recorded net on the condensed consolidated balance sheets. As of June 30, 2019, long-term deferred revenue included $102.9 million related to the U.S./RoW and China Agreement, which represents the net of $152.9 million of deferred revenue presented above and the above-mentioned $50.0 million unbilled contract asset. The revenue recognized under the U.S./RoW Agreement for the three months ended June 30, 2019 included an increase in revenue of $41.9 million resulting from changes to estimated variable consideration in the current period 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 $149.4 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. Other Revenues Other revenues consist primarily of collagen material sold for research purposes. Other revenues were immaterial for all periods presented. Deferred Revenue Deferred revenue represents amounts billed, or in certain cases, yet to be 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. Deferred revenue 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. As of December 31, 2018, such deferred revenue was included in long-term deferred revenue. As of June 30, 2019, following receipt of the Chinese Good Manufacturing Practices license by FibroGen Beijing in the second quarter of 2019, approximately $0.5 million of the related deferred revenue was included in short-term deferred revenue, which represents the amount of deferred revenue associated with the China unit of accounting that is expected to be recognized as a result of the transfer of control of commercial drug product in China.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. Fair Value Measurements The fair values of the Company’s financial assets that are measured on a recurring basis are as follows (in thousands): June 30, 2019 Level 1 Level 2 Level 3 Total US treasury notes and bills $ 350,891 $ 125,263 $ — $ 476,154 Bond and mutual funds 10,677 — — 10,677 Equity investments 237 — — 237 Money market funds 33,804 — — 33,804 Term deposit — 80,000 — 80,000 Certificate of deposit — 30,021 — 30,021 Total $ 395,609 $ 235,284 $ — $ 630,893 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 Our 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): June 30, 2019 Level 1 Level 2 Level 3 Total Lease obligations $ — $ — $ 1,745 $ 1,745 December 31, 2018 Level 1 Level 2 Level 3 Total Lease obligations $ — $ — $ 98,105 $ 98,105 The fair values 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. As of December 31, 2018, the Company had $96.2 million in lease obligations related to its building leases under build-to-suit arrangements. Upon the adoption of ASC 842 as of January 1, 2019, using the modified retrospective transition method, the Company derecognized these liabilities previously recognized under ASC 840 build-to-suit designation. Refer to Note 1 for details. The remaining balance of $1.7 million as of June 30, 2019 under lease obligations is related to an expansion option in the Company’s long-term property lease with Shorenstein Properties LLC (“Alexandria” or “landlord”). This expansion option allowed the Company to occupy part of an adjacent building within 31 months of the lease commencement date in 2008. In 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 that is financed over the remaining lease term to 2023. There were no transfers of assets or liabilities between levels for any of the periods presented.

Leases

Leases	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Leases	4. Leases The Company currently has two building leases treated as finance leases. In 2006, the Company entered into a long-term property lease with Alexandria for its corporate headquarters in San Francisco, California, with an initial term of 15 years, scheduled to expire in 2023. The Company has an option to extend the lease for an additional 10 years through 2033. The lease contract provides for a fixed annual rent, with scheduled increases of two percent that occur on each anniversary of the rent commencement date. This lease requires the Company to pay all costs of ownership, operation, and maintenance of the premises, including without limitation all operating costs, insurance costs, and taxes. In 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 building is leased for an initial lease term of eight years, scheduled to expire in 2021. Renewal options are not specified within the lease contract. The lease contract provides for fixed quarterly rent payments, with scheduled increases that occur as detailed in the lease contract. This lease requires the Company to pay all operating and maintenance costs, and a fixed amount for property management fees. The Company currently has five additional real estate leases for space within a building, which are treated as operating leases. These leases have lease terms ranging from two to four years. These lease contracts provide for fixed quarterly rent payments, and require the Company to pay operating and maintenance costs, and a fixed amount for property management fees. In addition, the Company has several immaterial lease arrangements for office equipment, scientific devices and automobile leases, with contracted lease terms ranging from two to five years, treated as finance leases or operating leases, respectively. The Company’s lease assets and related lease liabilities were as follows (in thousands): Balance Sheet Line Item June 30, 2019 Assets Finance: Right-of-use assets - cost $ 49,676 Accumulated amortization (5,140 ) Finance lease right-of-use assets, net Finance lease right-of-use assets 44,536 Operating: Right-of-use assets - cost 1,212 Accumulated amortization (273 ) Operating lease right-of-use assets, net Other assets 939 Total lease assets $ 45,475 Liabilities Current: Finance lease liabilities Finance lease liabilities, current $ 12,071 Operating lease liabilities Accrued and other current liabilities 591 Non-current: Finance lease liabilities Finance lease liabilities, non-current 43,780 Operating lease liabilities Other long-term liabilities 346 Total lease liabilities $ 56,788 The components of lease expense were as follows (in thousands): Statement of Operations Line Item Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Finance lease cost: Amortization of right-of-use assets Selling, general and administrative expenses $ 2,571 $ 5,140 Interest on lease liabilities Interest expense 609 1,249 Operating lease cost Research and development, Selling, general and administrative expenses 163 289 Sublease income Selling, general and administrative expenses (237 ) (824 ) Total lease cost $ 3,106 $ 5,854 Supplemental cash flow information related to leases were as follows (in thousands): Six Months Ended June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 191 Operating cash flows from finance leases 1,053 Financing cash flows from finance leases 5,850 Right-of-use assets obtained in exchange for new lease liabilities: Finance leases 49,676 Operating leases $ 1,212 Lease term and discount rate were as follows at June 30, 2019: June 30, 2019 Weighted-average remaining lease term (years): Finance leases 4.1 Operating leases 1.4 Weighted-average discount rate: Finance leases 4.43 % Operating leases 4.74 % Maturities of lease liabilities are as follows: Year Ending Finance Leases Operating Leases 2019 (Remaining six month period) $ 7,002 $ 313 2020 14,089 507 2021 13,678 134 2022 13,878 19 2023 12,523 — Total future lease payments 61,170 973 Less: Interest (5,319 ) (36 ) Present value of lease liabilities $ 55,851 $ 937 The following information was previously disclosed under ASC 840 as of December 31, 2018: Future minimum lease payments under all non-cancelable operating lease obligations as of December 31, 2018 were as follows (in thousands): Year Ending Operating Leases 2019 $ 444 2020 232 2021 25 2022 16 2023 — Total minimum payments $ 717 Future minimum lease payments, on a consolidated basis, under the Company’s facility lease financing obligations as of December 31, 2018 were 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

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2019
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): June 30, 2019 December 31, 2018 Cash $ 40,783 $ 38,783 US treasury notes and bills — 49,934 Money market funds 33,804 541 Total cash and cash equivalents $ 74,587 $ 89,258 At June 30, 2019 and December 31, 2018, a total of $26.0 million and $21.9 million, respectively, of the Company’s cash and cash equivalents were held outside of the U.S. in its foreign subsidiaries to be used primarily for its 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. The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s available-for-sale investments by major investments type are summarized in the tables below (in thousands): June 30, 2019 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value US treasury notes and bills $ 475,126 $ 1,028 $ — $ 476,154 Term deposit 80,000 — — 80,000 Certificates of deposit 30,000 21 — 30,021 Bond and mutual funds 10,602 75 — 10,677 Equity investments 125 112 — 237 Total investments $ 595,853 $ 1,236 $ — $ 597,089 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 At June 30, 2019, all of the available-for-sale investments had contractual maturities within one year. 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 and six months ended June 30, 2019 and 2018, the Company did not recognize any other-than-temporary impairment loss. Inventories Inventories consisted of the following (in thousands): June 30, 2019 Raw materials $ 797 Work-in-progress 1,035 Finished goods 149 Total inventories $ 1,981 The Company started capitalizing inventory costs in June 2019 when FibroGen China began productions of roxadustat for commercial sales purposes. There was no provision to write-down excess and obsolete inventory for the three months ended June 30, 2019. Prepaid expenses and other current assets Prepaid expenses and other current assets consisted of the following (in thousands): June 30, 2019 December 31, 2018 Unbilled contract assets $ 180,000 $ — Deferred revenues from associated contracts (52,019 ) — Net unbilled contract assets 127,981 — Prepaid assets 4,716 2,705 Other current assets 3,899 2,224 Total prepaid expenses and other current assets $ 136,596 $ 4,929 The unbilled contract assets as of June 30, 2019 were related to two regulatory milestones totaling $130.0 million under the Europe Agreement with Astellas associated with the planned MAA submission in Europe, and a $50.0 million regulatory milestone under the U.S./RoW Agreement with AstraZeneca associated with the planned NDA submission in the U.S. See Note 2 for details. Property and Equipment Property and equipment consisted of the following (in thousands): June 30, 2019 December 31, 2018 Leasehold improvements $ 101,250 $ 101,200 Building shell — 53,880 Laboratory equipment 16,754 16,405 Machinery 8,461 8,382 Computer equipment 6,655 6,473 Furniture and fixtures 5,778 5,690 Construction in progress 1,888 367 Total property and equipment $ 140,786 $ 192,397 Less: accumulated depreciation (95,921 ) (65,199 ) Property and equipment, net $ 44,865 $ 127,198 As of December 31, 2018, the Company had $53.9 million building shell cost and $13.5 million accumulated depreciation related to its building leases under build-to-suit arrangements. Upon the adoption of ASC 842 as of January 1, 2019, using the modified retrospective transition method, the Company derecognized these assets previously recognized under ASC 840 build-to-suit designation. Up to December 31, 2018, the leasehold improvements related to these building leases were depreciated over the life of the building under ASC 840. Upon the adoption of ASC 842, these leasehold improvements should have a useful life based on the lease term. As a result, at the adoption date, the Company recorded a cumulative adjustment of $38.9 million to the accumulated depreciation for these leasehold improvements so that their net balance equals the undepreciated amount had the useful life of the leasehold improvements always been equal to the lease terms. Refer to Note 1 for details. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): June 30, 2019 December 31, 2018 Preclinical and clinical trial accruals $ 41,104 $ 35,413 Payroll and related accruals 14,001 21,430 Property taxes and other 1,778 1,095 Professional services 3,588 2,648 Other 6,074 5,537 Total accrued liabilities $ 66,545 $ 66,123

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	6. Stock-Based Compensation Stock-based compensation expense was allocated to research and development and selling, general and administrative expense as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Research and development $ 10,450 $ 7,894 $ 20,028 $ 14,264 Selling, general and administrative 7,192 5,337 14,044 9,845 Total stock-based compensation expense $ 17,642 $ 13,231 $ 34,072 $ 24,109 The assumptions used to estimate the fair value of stock options granted and purchases under the Company’s 2014 Employee Share Purchase Plan (“ESPP”) using the Black-Scholes option valuation model were as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Stock Options Expected term (in years) 5.3 5.4 5.3 5.4 Expected volatility 68.2 % 67.5 % 67.9 % 67.8 % Risk-free interest rate 2.0 % 2.8 % 2.5 % 2.7 % Expected dividend yield — — — — Weighted average estimated fair value $ 24.40 $ 31.35 $ 33.20 $ 32.12 ESPPs Expected term (in years) 0.5 - 2.0 0.5 - 2.0 0.5 - 2.0 0.5 - 2.0 Expected volatility 48.1 - 62.1 % 47.3 - 75.3 % 48.1 - 62.1 % 47.3 - 75.3 % Risk-free interest rate 1.3 - 2.9 % 0.8 - 2.6 % 1.3 - 2.9 % 0.8 - 2.6 % Expected dividend yield — — — — Weighted average estimated fair value $ 19.07 $ 15.25 $ 19.65 $ 13.67

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	7. Income Taxes The provisions for income taxes for the three and six months ended June 30, 2019 and 2018 were due to foreign taxes. Based upon the weight of available evidence, which includes its historical operating performance, reported cumulative net losses since inception, the Company has established and continues to maintain a full valuation allowance against its deferred tax assets as it does not currently believe that realization of those assets is more likely than not.

Related Party Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2019
Related Party Transactions [Abstract]
Related Party Transactions	8. Related Party Transactions Astellas is an equity investor in the Company and considered a related party. The Company recorded revenue related to collaboration agreements with Astellas of $134.7 million and $139.6 million for the three and six months ended June 30, 2019, respectively, and $20.5 million and $25.6 million for the three and six months ended June 30, 2018, respectively. The Company recorded expense related to collaboration agreements with Astellas of $0.8 million and $0.2 million during the three months ended June 30, 2019 and 2018, respectively, and $1.3 million and $0.7 million during the six months ended June 30, 2019 and 2018. As of June 30, 2019 and December 31, 2018, accounts receivable from Astellas were $4.3 million and $47.2 million, respectively, and amounts due to Astellas were $0.8 million and $0.4 million, respectively. 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, pursuant to an amendment to the Japan Agreement that will allow Astellas to manufacture roxadustat drug product for commercialization in Japan. This amount was received during the first quarter of 2019. Prepaid expenses and other current assets as of June 30, 2019 included $128.0 million of net unbilled contract asset, representing a $130.0 million unbilled contract asset related to two regulatory milestones under the Europe Agreement with Astellas associated with the planned MAA submission to the EMA, net of $2.0 million of associated deferred revenue. See Note 2 for details. According to the Europe Agreement, this $130.0 million is not billable to Astellas until the submission of an MAA, therefore the net contract asset was included in the prepaid expenses and other current assets line on the Company’s condensed consolidated balance sheet as of June 30, 2019. There was no such contract asset balance as of December 31, 2018.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2019
Accounting Policies [Abstract]
Description of Operations	Description of Operations FibroGen, Inc. (“FibroGen” or the “Company”), incorporated in 1993 in Delaware and headquartered in San Francisco, California, with subsidiary offices in Beijing and Shanghai, People’s Republic of China (“China”), is a leading biopharmaceutical company discovering and developing a pipeline of first-in-class therapeutics. The Company applies its pioneering expertise in hypoxia-inducible factor (“HIF”), connective tissue growth factor (“CTGF”) biology, and clinical development to advance innovative medicines for the treatment of anemia, fibrotic disease, and cancer. Roxadustat, the Company’s most advanced product candidate, is an oral small molecule inhibitor of HIF prolyl hydroxylase (“HIF-PH”) activity, completing Phase 3 clinical development worldwide for the treatment of anemia in chronic kidney disease (“CKD”), with a New Drug Application (“NDA”) now approved by the National Medical Products Administration (“NMPA”) in China. The Company and its collaboration partners AstraZeneca AB (“AstraZeneca”) and Astellas Pharma Inc. (“Astellas”) are in the process of preparing an NDA for submission to the United States (“U.S.”) Food and Drug Administration (“FDA”) and a Marketing Authorization Application (“MAA”) for submission to the European Medicines Agency (“EMA”) this year. Astellas submitted an NDA for the treatment of anemia in CKD patients on dialysis in Japan in September 2018, which is currently under review by the Pharmaceuticals and Medical Devices Agency (“PMDA”). Roxadustat is in Phase 3 clinical development in the U.S. and Europe and in Phase 2/3 development in China for anemia associated with myelodysplastic syndromes (“MDS”). Pamrevlumab, an anti-CTGF human monoclonal antibody, is in Phase 3 clinical development for the treatment of idiopathic pulmonary fibrosis (“IPF”), and advancing towards Phase 3 for the treatment of pancreatic cancer. Pamrevlumab is also currently in a Phase 2 trial for Duchenne muscular dystrophy (“DMD”). FibroGen is also developing a biosynthetic cornea in China.
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The condensed consolidated financial statements include the accounts of FibroGen, its wholly owned subsidiaries and its majority-owned subsidiaries, FibroGen Europe Oy 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. The unaudited condensed consolidated financial statements and related disclosures have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”) applicable to interim financial reporting and with the instructions to Form 10-Q and Rule 10-01 of Regulation S-X of the U.S. Securities and Exchange Commission (“SEC”) and, therefore, do not include all information and footnote disclosures normally included in the annual consolidated financial statements. The financial information included herein should be read in conjunction with the consolidated financial statements and related notes in the Company’s Annual Report on Form 10-K filed with the SEC for the year ended December 31, 2018 (“2018 Form 10-K”). The accounting policies used by the Company in its presentation of interim financial results are consistent with those presented in Note 2 to the consolidated financial statements included in the 2018 Form 10-K, except for the following:
Leases	Leases The Company determines if an arrangement is a lease at inception date when it is given control of the underlying assets. The Company elected the practical expedient not to apply the lease recognition and measurement requirements to short-term leases, which is any lease with a term of 12 months or less as of the commencement date that does not include an option to purchase the underlying asset that the lessee is reasonably certain to exercise. The Company’s building leases previously accounted for as build-to-suit arrangements prior to the adoption of Accounting Standards Codification (“ASC”) 842 - Leases Lease right-of-use (“ROU”) assets and lease liabilities are recognized based on the present value of the future minimum lease payments over the lease term at commencement date. As its leases do not typically provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of future payments. The Company will reassess the incremental borrowing rate periodically for application to any new leases or lease modifications or if any company-specific or general business conditions warrant. Lease ROU assets include any lease payments made and initial direct costs incurred. The Company has lease agreements with lease and non-lease components. The Company generally accounts for each lease component separately from the non-lease components, and excludes all non-lease components from the calculation of minimum lease payments in measuring the ROU asset and lease liability . The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease terms. Regarding leases denominated in a foreign currency, the related ROU assets and the corresponding ROU asset amortization costs are remeasured using the exchange rate in effect at the date of initial recognition; the related lease liabilities are remeasured using the exchange rate in effect at the end of the reporting period; the lease costs and interest expenses related to lease liability accretion are remeasured using average exchange rates for the reporting period. Finance leases are included in finance lease ROU assets, finance lease liabilities, current and non-current on the Company’s consolidated balance sheets. Operating leases are included in other assets, accrued and other current liabilities, and other long-term liabilities on the Company’s consolidated balance sheets.
Inventories	Inventories Inventories are stated at the lower of cost and net realizable value. The cost of inventories are determined using full absorption and standard costing, which approximates cost based on a first-in, first-out method. The Company reviews the standard costs of raw materials, work-in-process and finished goods periodically, and at least annually, to ensure that its inventories approximate current actual costs. The cost of inventories includes direct material costs, direct labor and manufacturing overhead. The Company regularly reviews the need to adjust the carrying value of excess and obsolete inventories to their estimated net realizable value, if less than cost, based primarily on its estimated forecast of product demand and product expiration period.
Use of Estimates	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 and deferred 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. In the Company’s opinion, the accompanying unaudited condensed consolidated financial statements include all normal recurring adjustments necessary for a fair statement of its financial position, results of operations and cash flows for the interim periods presented.
Net Income (Loss) per Share	Net Income (Loss) per Share The following is a reconciliation of the basic and diluted net income (loss) per share calculation for the periods presented (in thousands, except per share data): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Net income (loss) $ 116,003 $ (23,421 ) $ 70,592 $ (64,817 ) Weighted average shares used to compute net income (loss) per share: Basic 86,445 83,750 86,077 83,309 Dilutive effect of potential common shares 5,283 — 5,992 — Diluted 91,728 83,750 92,069 83,309 Net income (loss) per share: Basic $ 1.34 $ (0.28 ) $ 0.82 $ (0.78 ) Diluted $ 1.26 $ (0.28 ) $ 0.77 $ (0.78 ) Diluted shares did not include 4.4 million and 3.4 million securities for the three and six months ended June 30, 2019, and 8.8 million and 8.7 million securities for the three and six months ended June 30, 2018, respectively, as they were anti-dilutive.
Recently Issued and Adopted Accounting Guidance	Recently Issued and Adopted Accounting Guidance ASC 842 In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842) Leases (Topic 842): Targeted Improvements The Company adopted the above guidance under ASC 842 as of January 1, 2019, using the modified retrospective transition method, through a cumulative-effect adjustment at the beginning of the first quarter of 2019. The Company elected the optional transition method under the guidance, which allowed it to continue applying previous lease guidance (ASC 840) for the comparative prior year periods presentation in the year of adoption. Accordingly, the Company recognized a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. In addition, the Company elected the package of transitional practical expedients permitted under the transition guidance under ASC 842, which among other things allows the Company to carry forward its historical lease classification, and not to reassess initial direct costs for any existing leases. Meanwhile, the Company did not elect the hindsight practical expedient because it has limited number of leases, lease terms are straightforward, and most of its lease renewals are undefined until negotiated. In addition, the Company has elected the short term accounting policy practical expedient and does not apply the balance sheet recognition requirements for short-term leases (excluding expenses relating to leases with a lease term of one month or less), by class of underlying asset to which the right of use relates. The Company has not elected the non-lease components practical expedient, and therefore accounts for each lease component separately from the non-lease components. Upon adoption of ASC 842, the Company classified its existing building leases that were previously accounted for as build-to-suit arrangements as finance leases, and applied the transition guidance. Accordingly, the Company derecognized the assets and liabilities previously recognized under ASC 840 build-to-suit guidance. In addition, as a result of applying the transition guidance, the Company also recorded an adjustment to the accumulated depreciation of related leasehold improvements to reflect a change in estimated useful life from the building life to the shorter of the building life and remaining lease term. Differences between the assets and liabilities derecognized were recorded to the opening balance of retained earnings. The impacts to the select line items from the Company’s condensed consolidated balance sheet upon adoption of the ASC 842 guidance are as follows (in thousands): Balance Sheet Line Item Nature of Adjustment New Lease Guidance Adoption Adjustment Assets Property and equipment, net Derecognition - build-to-suit lease assets - building shell, cost $ (53,880 ) Derecognition - build-to-suit lease assets - building shell, accumulated depreciation 13,476 Change of useful life - leasehold improvements, accumulated depreciation (38,877 ) Finance lease right-of-use assets Recognition - finance lease ROU assets 49,597 Other assets Recognition - operating lease ROU assets 730 Liabilities Accrued and other current liabilities Derecognition - deferred rent, current (619 ) Derecognition - build-to-suit lease liabilities, current (545 ) Recognition - operating lease liabilities, current 404 Finance lease liabilities, current Recognition - finance lease liabilities, current 11,499 Long-term portion of lease obligations Derecognition - build-to-suit lease liabilities, non-current (95,613 ) Deferred rent Derecognition - deferred rent, non-current (3,038 ) Finance lease liabilities, non-current Recognition - finance lease liabilities, non-current 49,884 Other long-term liabilities Recognition - operating lease liabilities, non-current 250 Stockholders’ equity Accumulated deficit Cumulative decrease to accumulated deficit $ 8,688 The adoption of this guidance did not have a material impact to the Company’s condensed consolidated statement of operations or condensed consolidated statement of cash flows for the six months ended June 30, 2019. ASU 2018-02 In February 2018, the FASB issued ASU 2018-02, Income Statement - Reporting Comprehensive Income: Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income Accumulated Other Comprehensive Loss Accumulated Deficit Balance at December 31, 2018 $ (2,281 ) $ (715,827 ) Impact of change in accounting principle upon adoption of ASU 2018-02 611 (611 ) Opening balance as of January 1, 2019 $ (1,670 ) $ (716,438 ) The adoption of this guidance had no impact to the Company’s condensed consolidated statement of operations or condensed consolidated statement of cash flows for the six months ended June 30, 2019. SEC Disclosure Requirement In August 2018, the SEC adopted the final rule under SEC Release No. 33-10532, “Disclosure Update and Simplification,” ASU 2018-07 In June 2018, the FASB issued ASU 2018-07, Compensation - Stock Compensation (Topic 718): Improvements to Nonemployee Share-Based Payment Accounting.
Recently Issued Accounting Guidance Not Yet Adopted	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. 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. In June 2016, the FASB issued ASU 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments Codification Improvements to Topic 326, Financial Instruments—Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments Financial Instruments – Credit Losses (Topic 326): Targeted Transition Relief
Collaboration Arrangements	Astellas Agreements Japan Agreement In June 2005, the Company entered into a collaboration agreement with 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). Under the Japan Agreement, the Company is also eligible to receive from Astellas an aggregate of approximately $132.5 million in potential milestone payments, comprised of (i) up to $22.5 million in milestone payments upon achievement of specified clinical and development milestone events (such amounts were fully received as of July 2016), (ii) up to $95.0 million in milestone payments upon achievement of specified regulatory milestone events, and (iii) up to approximately $15.0 million in milestone payments upon the achievement of specified commercial sales milestone. The aggregate amount of such consideration received through June 30, 2019 totals $77.6 million. 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). Under the Europe Agreement, the Company is also eligible to receive from Astellas an aggregate of approximately $425.0 million in potential milestone payments, comprised of (i) up to $90.0 million in milestone payments upon achievement of specified clinical and development milestone events (such amounts were fully received as of 2012), (ii) up to $335.0 million in milestone payments upon achievement of specified regulatory milestone events. 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. The aggregate amount of such consideration received through June 30, 2019 totals $410.0 million. 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 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 AstraZeneca and Astellas. 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. During the second quarter of 2019, the Company received positive topline results from analyses of pooled major adverse cardiac event (“MACE”) and MACE+ data from its Phase 3 trials evaluating roxadustat as a treatment for dialysis and non-dialysis CKD patients, enabling Astellas to prepare for an MAA submission to the EMA during their fiscal year 2019, which ends on March 31, 2020, following the Company’s NDA submission to the FDA. The Company evaluated the two regulatory milestone payments associated with the planned MAA submission and concluded that these milestones became probable of being achieved in the second quarter of 2019. Accordingly, the total consideration of $130.0 million associated with these milestones was included in the transaction price and allocated to performance obligations under the Europe Agreement in the second quarter of 2019, of which $129.5 million was recognized as revenue during the period from performance obligations satisfied or partially satisfied as of June 30, 2019. According to the Europe Agreement, these milestone payments are not billable to Astellas until the submission of an MAA, therefore this $130.0 million was recorded as an unbilled contract asset as of June 30, 2019. AstraZeneca Agreements U.S./Rest of World (“RoW”) 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 paid upfront, non-contingent, non-refundable and time-based payments totaling $374.0 million (such amounts were fully received as of June 2016). Under the U.S./RoW Agreement, the Company is also eligible to receive from AstraZeneca an aggregate of approximately $875.0 million in potential milestone payments, comprised of (i) up to $65.0 million in milestone payments upon achievement of specified clinical and development milestone events, $15.0 million of which was received in 2015 as a result of the finalization of its two audited pre-clinical carcinogenicity study reports, (ii) up to $325.0 million in milestone payments upon achievement of specified regulatory milestone events, (iii) up to $160.0 million in milestone payments related to activity by potential competitors and (iv) up to approximately $325.0 million in milestone payments upon the achievement of specified commercial sales events. The aggregate amount of such consideration received through June 30, 2019 totals $389.0 million. As mentioned above, during the second quarter of 2019, the Company received positive topline results from analyses of pooled MACE and MACE+ data from its Phase 3 trials for roxadustat, enabling the Company’s NDA submission to the FDA. The Company evaluated the regulatory milestone payment associated with this planned NDA submission and concluded that this milestone became probable of being achieved in the second quarter of 2019. Accordingly, the consideration of $50.0 million associated with this milestone was included in the transaction price and allocated to performance obligations under the U.S./ RoW Agreement in the second quarter of 2019, of which $41.6 million was recognized as revenue during the period from performance obligations satisfied or partially satisfied as of June 30, 2019. According to the U.S/RoW Agreement, this milestone payment is not billable to AstraZeneca until the Company has submitted the NDA, therefore this $50.0 million was recorded as an unbilled contract asset as of June 30, 2019. 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 paid upfront, non-contingent and non-refundable payments totaling $28.2 million (such amounts were fully received in 2014). Under the China Agreement, the Company is also eligible to receive from AstraZeneca an aggregate of approximately $348.5 million in potential milestone payments, comprised of (i) up to $15.0 million in milestone payments upon achievement of specified clinical and development milestone events, (ii) up to $146.0 million in milestone payments upon achievement of specified regulatory milestone events, and (iii) up to approximately $187.5 million in milestone payments upon the achievement of specified commercial sales and other events. 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. The aggregate amount of such consideration received through June 30, 2019 totals $55.2 million. 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 AstraZeneca and Astellas. 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. On December 17, 2018, FibroGen (China) Medical Technology Development Co., Ltd. (“FibroGen Beijing”), received marketing authorization from the NMPA for roxadustat, a first-in-class HIF-PH 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 Beijing 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. These milestones payments were received in the first quarter of 2019.
Other Revenues	Other Revenues Other revenues consist primarily of collagen material sold for research purposes. Other revenues were immaterial for all periods presented.
Deferred Revenue	Deferred Revenue Deferred revenue represents amounts billed, or in certain cases, yet to be 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. Deferred revenue 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. As of December 31, 2018, such deferred revenue was included in long-term deferred revenue. As of June 30, 2019, following receipt of the Chinese Good Manufacturing Practices license by FibroGen Beijing in the second quarter of 2019, approximately $0.5 million of the related deferred revenue was included in short-term deferred revenue, which represents the amount of deferred revenue associated with the China unit of accounting that is expected to be recognized as a result of the transfer of control of commercial drug product in China.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2019
Summary of Reconciliation of Basic and Diluted Net Income (Loss) Per Share Calculation	The following is a reconciliation of the basic and diluted net income (loss) per share calculation for the periods presented (in thousands, except per share data): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Net income (loss) $ 116,003 $ (23,421 ) $ 70,592 $ (64,817 ) Weighted average shares used to compute net income (loss) per share: Basic 86,445 83,750 86,077 83,309 Dilutive effect of potential common shares 5,283 — 5,992 — Diluted 91,728 83,750 92,069 83,309 Net income (loss) per share: Basic $ 1.34 $ (0.28 ) $ 0.82 $ (0.78 ) Diluted $ 1.26 $ (0.28 ) $ 0.77 $ (0.78 )
ASU 2016-02 [Member]
Schedule of Impacts Upon Adoption of New Guidance	The impacts to the select line items from the Company’s condensed consolidated balance sheet upon adoption of the ASC 842 guidance are as follows (in thousands): Balance Sheet Line Item Nature of Adjustment New Lease Guidance Adoption Adjustment Assets Property and equipment, net Derecognition - build-to-suit lease assets - building shell, cost $ (53,880 ) Derecognition - build-to-suit lease assets - building shell, accumulated depreciation 13,476 Change of useful life - leasehold improvements, accumulated depreciation (38,877 ) Finance lease right-of-use assets Recognition - finance lease ROU assets 49,597 Other assets Recognition - operating lease ROU assets 730 Liabilities Accrued and other current liabilities Derecognition - deferred rent, current (619 ) Derecognition - build-to-suit lease liabilities, current (545 ) Recognition - operating lease liabilities, current 404 Finance lease liabilities, current Recognition - finance lease liabilities, current 11,499 Long-term portion of lease obligations Derecognition - build-to-suit lease liabilities, non-current (95,613 ) Deferred rent Derecognition - deferred rent, non-current (3,038 ) Finance lease liabilities, non-current Recognition - finance lease liabilities, non-current 49,884 Other long-term liabilities Recognition - operating lease liabilities, non-current 250 Stockholders’ equity Accumulated deficit Cumulative decrease to accumulated deficit $ 8,688
ASU 2018-02 [Member]
Schedule of Impacts Upon Adoption of New Guidance	The impacts, based on the aggregate portfolio approach, 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, 2018 $ (2,281 ) $ (715,827 ) Impact of change in accounting principle upon adoption of ASU 2018-02 611 (611 ) Opening balance as of January 1, 2019 $ (1,670 ) $ (716,438 )

Collaboration Agreements (Table

Collaboration Agreements (Tables)	6 Months Ended
	Jun. 30, 2019
Japan [Member]
Summary of Revenue Recognized under Agreement	Amounts recognized as revenue under the Japan Agreement were as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, Agreement Performance Obligation 2019 2018 2019 2018 Japan License revenue $ — $ 14,323 $ — $ 14,323 Development revenue $ 369 $ 1,142 $ 615 $ 1,591
Transaction Price Related to Consideration Received and Accounts Receivable Allocated to Performance Obligations along with Associated Deferred Revenue	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 June 30, 2019 Deferred Revenue at June 30, 2019 Total Consideration Through June 30, 2019 License $ 74,089 $ — $ 74,089 Development revenue 14,523 136 14,659 Total license and development revenue $ 88,612 $ 136 $ 88,748
Europe [Member]
Summary of Revenue Recognized under Agreement	Amounts recognized as revenue under the Europe Agreement were as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, Agreement Performance Obligation 2019 2018 2019 2018 Europe License revenue $ 117,470 $ — $ 117,470 $ — Development revenue $ 16,854 $ 5,003 $ 21,467 $ 9,726
Transaction Price Related to Consideration Received and Accounts Receivable Allocated to Performance Obligations along with Associated Deferred Revenue	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 June 30, 2019 Deferred Revenue at June 30, 2019 Total Consideration Through June 30, 2019 License $ 487,951 $ — $ 487,951 Development revenue 224,304 2,019 226,323 Total license and development revenue $ 712,255 $ 2,019 * $ 714,274 _______________________________________________________________________________________________________ * Contract assets and liabilities related to rights and obligations in the same contract are recorded net on the condensed consolidated balance sheets. As of June 30, 2019, prepaid expenses and other current assets included a net unbilled contract asset of $128.0 million related to the Europe Agreement, which represents the net of the above-mentioned unbilled contract asset of $130.0 million, and $2.0 million of deferred revenue presented above.
U.S./RoW and China [Member]
Summary of Revenue Recognized under Agreement	Amounts recognized as revenue under the U.S./RoW Agreement were as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, Agreement Performance Obligation 2019 2018 2019 2018 U.S. / RoW and China License revenue $ 33,111 $ — $ 33,111 $ — Development revenue 23,762 23,479 42,766 50,202 China performance obligation $ — $ — $ — $ —
Transaction Price Related to Consideration Received and Accounts Receivable Allocated to Performance Obligations along with Associated Deferred Revenue	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 June 30, 2019 Deferred Revenue at June 30, 2019 Total Consideration Through June 30, 2019 License $ 327,275 $ — $ 327,275 Co-development, information sharing & committee services 451,402 16,342 467,744 China performance obligation — 136,584 136,584 Total license and development revenue $ 778,677 $ 152,926 * $ 931,603 _______________________________________________________________________________________________________ * Contract assets and liabilities related to rights and obligations in the same contract are recorded net on the condensed consolidated balance sheets. As of June 30, 2019, long-term deferred revenue included $102.9 million related to the U.S./RoW and China Agreement, which represents the net of $152.9 million of deferred revenue presented above and the above-mentioned $50.0 million unbilled contract asset.

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2019
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): June 30, 2019 Level 1 Level 2 Level 3 Total US treasury notes and bills $ 350,891 $ 125,263 $ — $ 476,154 Bond and mutual funds 10,677 — — 10,677 Equity investments 237 — — 237 Money market funds 33,804 — — 33,804 Term deposit — 80,000 — 80,000 Certificate of deposit — 30,021 — 30,021 Total $ 395,609 $ 235,284 $ — $ 630,893 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
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): June 30, 2019 Level 1 Level 2 Level 3 Total Lease obligations $ — $ — $ 1,745 $ 1,745 December 31, 2018 Level 1 Level 2 Level 3 Total Lease obligations $ — $ — $ 98,105 $ 98,105

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2019
Leases [Abstract]
Schedule of Lease Assets and Related Lease Liabilities	The Company’s lease assets and related lease liabilities were as follows (in thousands): Balance Sheet Line Item June 30, 2019 Assets Finance: Right-of-use assets - cost $ 49,676 Accumulated amortization (5,140 ) Finance lease right-of-use assets, net Finance lease right-of-use assets 44,536 Operating: Right-of-use assets - cost 1,212 Accumulated amortization (273 ) Operating lease right-of-use assets, net Other assets 939 Total lease assets $ 45,475 Liabilities Current: Finance lease liabilities Finance lease liabilities, current $ 12,071 Operating lease liabilities Accrued and other current liabilities 591 Non-current: Finance lease liabilities Finance lease liabilities, non-current 43,780 Operating lease liabilities Other long-term liabilities 346 Total lease liabilities $ 56,788
Components of Lease Expense	The components of lease expense were as follows (in thousands): Statement of Operations Line Item Three Months Ended June 30, 2019 Six Months Ended June 30, 2019 Finance lease cost: Amortization of right-of-use assets Selling, general and administrative expenses $ 2,571 $ 5,140 Interest on lease liabilities Interest expense 609 1,249 Operating lease cost Research and development, Selling, general and administrative expenses 163 289 Sublease income Selling, general and administrative expenses (237 ) (824 ) Total lease cost $ 3,106 $ 5,854
Schedule of Supplemental Cash Flow Information Related to Leases	Supplemental cash flow information related to leases were as follows (in thousands): Six Months Ended June 30, 2019 Cash paid for amounts included in the measurement of lease liabilities: Operating cash flows from operating leases $ 191 Operating cash flows from finance leases 1,053 Financing cash flows from finance leases 5,850 Right-of-use assets obtained in exchange for new lease liabilities: Finance leases 49,676 Operating leases $ 1,212
Schedule of Lease Term and Discount Rate	Lease term and discount rate were as follows at June 30, 2019: June 30, 2019 Weighted-average remaining lease term (years): Finance leases 4.1 Operating leases 1.4 Weighted-average discount rate: Finance leases 4.43 % Operating leases 4.74 %
Schedule of Maturities of Finance and Operating Leases Liabilities	Maturities of lease liabilities are as follows: Year Ending Finance Leases Operating Leases 2019 (Remaining six month period) $ 7,002 $ 313 2020 14,089 507 2021 13,678 134 2022 13,878 19 2023 12,523 — Total future lease payments 61,170 973 Less: Interest (5,319 ) (36 ) Present value of lease liabilities $ 55,851 $ 937
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 were 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 were 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

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Cash and Cash Equivalents	Cash and cash equivalents consisted of the following (in thousands): June 30, 2019 December 31, 2018 Cash $ 40,783 $ 38,783 US treasury notes and bills — 49,934 Money market funds 33,804 541 Total cash and cash equivalents $ 74,587 $ 89,258
Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Available-for-Sale Investments	The Company’s investments consist of available-for-sale debt investments, marketable equity investments, a term deposit and a certificate of deposit. The amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s available-for-sale investments by major investments type are summarized in the tables below (in thousands): June 30, 2019 Amortized Cost Gross Unrealized Holding Gains Gross Unrealized Holding Losses Fair Value US treasury notes and bills $ 475,126 $ 1,028 $ — $ 476,154 Term deposit 80,000 — — 80,000 Certificates of deposit 30,000 21 — 30,021 Bond and mutual funds 10,602 75 — 10,677 Equity investments 125 112 — 237 Total investments $ 595,853 $ 1,236 $ — $ 597,089 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
Schedule of Inventory	Inventories consisted of the following (in thousands): June 30, 2019 Raw materials $ 797 Work-in-progress 1,035 Finished goods 149 Total inventories $ 1,981
Schedule of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consisted of the following (in thousands): June 30, 2019 December 31, 2018 Unbilled contract assets $ 180,000 $ — Deferred revenues from associated contracts (52,019 ) — Net unbilled contract assets 127,981 — Prepaid assets 4,716 2,705 Other current assets 3,899 2,224 Total prepaid expenses and other current assets $ 136,596 $ 4,929
Schedule of Property and Equipment	Property and equipment consisted of the following (in thousands): June 30, 2019 December 31, 2018 Leasehold improvements $ 101,250 $ 101,200 Building shell — 53,880 Laboratory equipment 16,754 16,405 Machinery 8,461 8,382 Computer equipment 6,655 6,473 Furniture and fixtures 5,778 5,690 Construction in progress 1,888 367 Total property and equipment $ 140,786 $ 192,397 Less: accumulated depreciation (95,921 ) (65,199 ) Property and equipment, net $ 44,865 $ 127,198
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): June 30, 2019 December 31, 2018 Preclinical and clinical trial accruals $ 41,104 $ 35,413 Payroll and related accruals 14,001 21,430 Property taxes and other 1,778 1,095 Professional services 3,588 2,648 Other 6,074 5,537 Total accrued liabilities $ 66,545 $ 66,123

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Allocated Stock-Based Compensation Expense	Stock-based compensation expense was allocated to research and development and selling, general and administrative expense as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Research and development $ 10,450 $ 7,894 $ 20,028 $ 14,264 Selling, general and administrative 7,192 5,337 14,044 9,845 Total stock-based compensation expense $ 17,642 $ 13,231 $ 34,072 $ 24,109
Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Purchases under 2014 Employee Share Purchase Plan	The assumptions used to estimate the fair value of stock options granted and purchases under the Company’s 2014 Employee Share Purchase Plan (“ESPP”) using the Black-Scholes option valuation model were as follows: Three Months Ended June 30, Six Months Ended June 30, 2019 2018 2019 2018 Stock Options Expected term (in years) 5.3 5.4 5.3 5.4 Expected volatility 68.2 % 67.5 % 67.9 % 67.8 % Risk-free interest rate 2.0 % 2.8 % 2.5 % 2.7 % Expected dividend yield — — — — Weighted average estimated fair value $ 24.40 $ 31.35 $ 33.20 $ 32.12 ESPPs Expected term (in years) 0.5 - 2.0 0.5 - 2.0 0.5 - 2.0 0.5 - 2.0 Expected volatility 48.1 - 62.1 % 47.3 - 75.3 % 48.1 - 62.1 % 47.3 - 75.3 % Risk-free interest rate 1.3 - 2.9 % 0.8 - 2.6 % 1.3 - 2.9 % 0.8 - 2.6 % Expected dividend yield — — — — Weighted average estimated fair value $ 19.07 $ 15.25 $ 19.65 $ 13.67

Significant Accounting Polici_4

Significant Accounting Policies - Additional Information (Detail) shares in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019shares	Jun. 30, 2018shares	Jun. 30, 2019Segmentshares	Jun. 30, 2018shares	Dec. 31, 2017
Accounting Policies [Abstract]
Number of operating segment | Segment			1
Short term investments maturity			12 months
Anti-dilutive shares | shares	4.4	8.8	3.4	8.7
U.S. federal statutory income tax rate			21.00%		35.00%

Significant Accounting Polici_5

Significant Accounting Policies - Summary of Reconciliation of Basic and Diluted Net Income (Loss) Per Share Calculation (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Net income (loss)	$ 116,003	$ (23,421)	$ 70,592	$ (64,817)
Weighted average number of common shares used to calculate net income (loss) per share:
Basic	86,445	83,750	86,077	83,309
Dilutive effect of potential common shares	5,283	0	5,992	0
Diluted	91,728	83,750	92,069	83,309
Net income (loss) per share:
Basic	$ 1.34	$ (0.28)	$ 0.82	$ (0.78)
Diluted	$ 1.26	$ (0.28)	$ 0.77	$ (0.78)

Summary of Significant Accounti

Summary of Significant Accounting Policies - Schedule of Impacts to Condensed Consolidated Balance Sheet Upon Adoption of 842 Guidance (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Assets
Property and equipment, net	$ 44,865	$ 127,198
Finance lease right-of-use assets	44,536	0
Liabilities, stockholders’ equity and non-controlling interests
Finance lease liabilities, current	12,071	0
Deferred rent	0	3,038
Finance lease liabilities, non-current	43,780	0
Accumulated deficit	(637,158)	$ (715,827)
Derecognition Build to Suit Lease Assets [Member] | Building Shell [Member]
Assets
Property and equipment, net	(53,880)
Derecognition Build to Suit Lease Assets Accumulated Depreciation [Member] | Building Shell [Member]
Assets
Property and equipment, net	13,476
Leasehold Improvements Accumulated Depreciation [Member]
Assets
Property and equipment, net	(38,877)
Recognition Finance Lease Assets [Member]
Assets
Finance lease right-of-use assets	49,597
Recognition Operating Lease Assets [Member]
Assets
Other assets	730
Derecognition Deferred Rent Current [Member]
Liabilities, stockholders’ equity and non-controlling interests
Accrued and other current liabilities	(619)
Derecognition Build to Suit Lease Liabilities Current [Member]
Liabilities, stockholders’ equity and non-controlling interests
Accrued and other current liabilities	(545)
Recognition Operating Lease Liabilities Current [Member]
Liabilities, stockholders’ equity and non-controlling interests
Accrued and other current liabilities	404
Recognition Finance Lease Liabilities Current [Member]
Liabilities, stockholders’ equity and non-controlling interests
Finance lease liabilities, current	11,499
Derecognition Build to Suit Lease Liabilities Non Current [Member]
Liabilities, stockholders’ equity and non-controlling interests
Long-term portion of lease obligations	(95,613)
Derecognition Deferred Rent Non Current [Member]
Liabilities, stockholders’ equity and non-controlling interests
Deferred rent	(3,038)
Recognition Finance Lease Liabilities Non Current [Member]
Liabilities, stockholders’ equity and non-controlling interests
Finance lease liabilities, non-current	49,884
Recognition Operating Lease Liabilities Non Current [Member]
Liabilities, stockholders’ equity and non-controlling interests
Other long-term liabilities	250
Cumulative Decrease to Accumulated Deficit [Member]
Liabilities, stockholders’ equity and non-controlling interests
Accumulated deficit	$ 8,688

Summary of Significant Accoun_2

Summary of Significant Accounting Policies - Schedule of Impacts to Accumulated Other Comprehensive Loss and Accumulated Deficit Upon Adoption of Guidance (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Accounting Policy [Line Items]
Accumulated other comprehensive loss	$ (462)		$ (2,281)
Accumulated deficit	$ (637,158)		$ (715,827)
ASU 2018-02 [Member]
Accounting Policy [Line Items]
Accumulated other comprehensive loss		$ (1,670)
Accumulated deficit		(716,438)
Impact of change in accounting principle upon adoption of ASU 2018-02 [Member] | ASU 2018-02 [Member]
Accounting Policy [Line Items]
Accumulated other comprehensive loss		611
Accumulated deficit		$ (611)

Collaboration Agreements - Aste

Collaboration Agreements - Astellas Agreements - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended		6 Months Ended	12 Months Ended	35 Months Ended	45 Months Ended
	Apr. 30, 2006	Jun. 30, 2005	Jun. 30, 2019	Dec. 31, 2018	Feb. 28, 2009	Feb. 28, 2009
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Unbilled contract asset			$ 180,000	$ 0
Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Unbilled contract asset			130,000
Astellas Agreement [Member] | Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received						$ 40,100
Potential milestone payments		$ 132,500
Commercial sales milestone		15,000
Aggregate consideration received			77,600
Astellas Agreement [Member] | Japan [Member] | Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments		22,500
Astellas Agreement [Member] | Japan [Member] | Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments		$ 95,000
Astellas Agreement [Member] | Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received					$ 320,000
Potential milestone payments	$ 425,000
Aggregate consideration received			$ 410,000
Percentage of joint development costs committed to fund	50.00%
Additional consideration based on net sales description			low 20% range
Estimated joint development extended service period				2023
Transaction price and allocated to performance obligations			$ 130,000
Revenue during period from performance obligations			129,500
Unbilled contract asset			$ 130,000
Astellas Agreement [Member] | Europe [Member] | Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments	$ 90,000
Astellas Agreement [Member] | Europe [Member] | Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments	$ 335,000

Collaboration Agreements - Astr

Collaboration Agreements - AstraZeneca Agreements - Additional Information 1 (Detail) - USD ($) $ in Thousands	Dec. 29, 2018	Dec. 17, 2018	Jul. 30, 2013	Jun. 30, 2019	Dec. 31, 2015	Dec. 31, 2018
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Unbilled contract asset				$ 180,000		$ 0
AstraZeneca Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Transaction price and allocated to performance obligations				50,000
Revenue during period from performance obligations				41,600
Unbilled contract asset				50,000
AstraZeneca Agreements [Member] | U.S./RoW [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent, non-refundable and time-based payments			$ 374,000
Potential milestone payments			875,000
Commercial sales milestone			325,000
Aggregate consideration received				389,000
Unbilled contract asset				50,000
AstraZeneca Agreements [Member] | U.S./RoW [Member] | Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			65,000
AstraZeneca Agreements [Member] | U.S./RoW [Member] | Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			325,000
AstraZeneca Agreements [Member] | U.S./RoW [Member] | Deferred Approval Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			160,000
AstraZeneca Agreements [Member] | U.S./RoW [Member] | Development Milestones [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Receipt of development milestone payment					$ 15,000
AstraZeneca Agreements [Member] | China [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			348,500
Aggregate consideration received				$ 55,200
Proceeds from upfront, non-contingent and non-refundable payments			28,200
Commercial sales and other events milestone			187,500
Estimated joint development extended service period				2024
Milestone payment, revenue recognition	$ 6,000	$ 6,000
AstraZeneca Agreements [Member] | China [Member] | Clinical and Development Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			15,000
AstraZeneca Agreements [Member] | China [Member] | Regulatory Milestone [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Potential milestone payments			$ 146,000

Collaboration Agreements - Summ

Collaboration Agreements - Summary of Revenue Recognized under Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	$ 191,566	$ 43,952	$ 215,429	$ 75,876
License Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	150,581	14,323	150,581	14,323
Development Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	40,985	29,629	64,848	61,553
Astellas Agreement [Member] | License Revenue [Member] | Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	0	14,323	0	14,323
Astellas Agreement [Member] | License Revenue [Member] | Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	117,470	0	117,470	0
Astellas Agreement [Member] | Development Revenue [Member] | Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	369	1,142	615	1,591
Astellas Agreement [Member] | Development Revenue [Member] | Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	16,854	5,003	21,467	9,726
AstraZeneca Agreements [Member] | China [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	0	0	0	0
AstraZeneca Agreements [Member] | License Revenue [Member] | U.S./RoW and China [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	33,111	0	33,111	0
AstraZeneca Agreements [Member] | Development Revenue [Member] | U.S./RoW and China [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total revenue	$ 23,762	$ 23,479	$ 42,766	$ 50,202

Collaboration Agreements - Tran

Collaboration Agreements - Transaction Price Related to Consideration Received and Accounts Receivable Allocated to Performance Obligations along with Associated Deferred Revenue (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Deferred Revenue	$ 52,019	$ 0
Astellas Agreement [Member] | Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	88,612
Deferred Revenue	136
Total Consideration	88,748
Astellas Agreement [Member] | Japan [Member] | Development Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	14,523
Deferred Revenue	136
Total Consideration	14,659
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] | Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	712,255
Deferred Revenue	2,019
Total Consideration	714,274
Astellas Agreement [Member] | Europe [Member] | Development Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	224,304
Deferred Revenue	2,019
Total Consideration	226,323
Astellas Agreement [Member] | Europe [Member] | License Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	487,951
Deferred Revenue	0
Total Consideration	487,951
AstraZeneca Agreements [Member] | U.S./RoW and China [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	778,677
Deferred Revenue	152,926
Total Consideration	931,603
AstraZeneca Agreements [Member] | U.S./RoW and China [Member] | License Revenue [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Cumulative Revenue	327,275
Deferred Revenue	0
Total Consideration	327,275
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	451,402
Deferred Revenue	16,342
Total Consideration	467,744
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	136,584
Total Consideration	$ 136,584

Collaboration Agreements - Su_2

Collaboration Agreements - Summary of Revenue Recognized Under the Collaboration Agreements - Additional Information 4 (Detail) $ in Millions	3 Months Ended
	Jun. 30, 2019USD ($)
Japan [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Remainder of transaction price, variable consideration from estimated future co-development billing	$ 0.5
Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Remainder of transaction price, variable consideration from estimated future co-development billing	9.4
Europe [Member] | Astellas Agreement [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Changes in revenue due to prior period adjustment of performance obligations	129.2
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	149.4
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	$ 41.9

Collaboration Agreements - Tr_2

Collaboration Agreements - Transaction Price Related to Consideration Received and Accounts Receivable Allocated to Performance Obligations along with Associated Deferred Revenue (Parenthetical) (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Unbilled contract asset	$ 180,000	$ 0
Deferred revenue	52,019	0
Net unbilled contract asset	127,981	0
Long-term deferred revenue	102,926	$ 136,109
Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Unbilled contract asset	130,000
Astellas Agreement [Member] | Europe [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Unbilled contract asset	130,000
Deferred revenue	2,019
Astellas Agreement [Member] | Europe [Member] | Prepaid Expenses and Other Current Assets [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Net unbilled contract asset	128,000
AstraZeneca Agreements [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Unbilled contract asset	50,000
AstraZeneca Agreements [Member] | U.S./RoW [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Unbilled contract asset	50,000
Deferred revenue	152,900
Net unbilled contract asset	50,000
Long-term deferred revenue	$ 102,900

Collaboration Agreements - Defe

Collaboration Agreements - Deferred Revenue - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Contract with Customer, Liability [Abstract]
Deferred revenue	$ 52,019	$ 0
AstraZeneca Agreements [Member] | China [Member]
Contract with Customer, Liability [Abstract]
Deferred revenue	$ 500

Fair Value Measurements - Fair

Fair Value Measurements - Fair Values of Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	$ 597,089	$ 587,964
US treasury notes and bills [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	476,154	467,336
Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	10,677	10,484
Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	237	234
Term deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	80,000	80,000
Certificate of deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	30,021	29,910
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	630,893	638,439
Fair Value, Measurements, Recurring [Member] | US treasury notes and bills [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	476,154	517,270
Fair Value, Measurements, Recurring [Member] | Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	10,677	10,484
Fair Value, Measurements, Recurring [Member] | Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	237	234
Fair Value, Measurements, Recurring [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	33,804	541
Fair Value, Measurements, Recurring [Member] | Term deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	80,000	80,000
Fair Value, Measurements, Recurring [Member] | Certificate of deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	30,021	29,910
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	395,609	303,576
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | US treasury notes and bills [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	350,891	292,317
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	10,677	10,484
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	237	234
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	33,804	541
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Term deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 1 [Member] | Certificate of deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	235,284	334,863
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | US treasury notes and bills [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	125,263	224,953
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Term deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	80,000	80,000
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Certificate of deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	30,021	29,910
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | US treasury notes and bills [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Bond and mutual funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Equity investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Term deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Certificate of deposit [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	$ 0	$ 0

Fair Value Measurements - Fai_2

Fair Value Measurements - Fair Values of Financial Liabilities Carried at Historical Cost (Detail) - Lease obligations [Member] - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 1,745	$ 98,105
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	$ 1,745	$ 98,105

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Lease payment liability	$ 55,851,000
Transfers of assets from level 1 to 2	0	$ 0
Transfers of assets from level 2 to 1	0	0
Transfers of liabilities from level 1 to 2	0	0
Transfers of liabilities from level 2 to 1	0	0
Transfers of assets into level 3	0	0
Transfers of assets out of level 3	0	0
Transfers of liabilities into level 3	0	0
Transfers of liabilities out of level 3	$ 0	0
Shorenstein Properties LLC [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Lease commencement date	2008
Lease payment liability	$ 5,000,000
Remaining lease term	2023
Building [Member] | Shorenstein Properties LLC [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Lease maximum expansion period	31 months
Lease obligations [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 1,745,000	98,105,000
Lease obligations [Member] | Long-term property lease [Member] | Shorenstein Properties LLC [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure	$ 1,700,000
Lease obligations [Member] | Building [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities fair value disclosure		$ 96,200,000

Leases - Additional Information

Leases - Additional Information (Detail) - Lease	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2013	Dec. 31, 2006
Minimum [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, lease term	2 years
Maximum [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, lease term	4 years
Shorenstein Properties LLC [Member]
Lessee Lease Description [Line Items]
Lessee, finance lease, initial lease term			15 years
Lessee, finance lease, expiration period			2023
Lessee, finance lease, option to extend the additional lease term			10 years
Lessee, finance lease, additional lease expiration period			2033
Percentage increases on each anniversary of rent commencement date			2.00%
Lessee, finance lease, existence of option to extend			true
Lessee, finance lease, option to extend	The Company has an option to extend the lease for an additional 10 years through 2033.
Beijing Economic-Technological Development Area [Member]
Lessee Lease Description [Line Items]
Lessee, finance lease, initial lease term		8 years
Lessee, finance lease, expiration period		2021
Lessee, finance lease, existence of option to extend		false
Building [Member]
Lessee Lease Description [Line Items]
Number of finance leases	2
Number of operating leases	5
Office Equipment [Member] | Minimum [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, lease term	2 years
Office Equipment [Member] | Maximum [Member]
Lessee Lease Description [Line Items]
Lessee, operating lease, lease term	5 years

Leases - Schedule of Lease Asse

Leases - Schedule of Lease Assets and Related Lease Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Leases [Abstract]
Right-of-use assets - cost	$ 49,676
Accumulated amortization	(5,140)
Finance lease right-of-use assets, net	44,536	$ 0
Right-of-use assets - cost	1,212
Accumulated amortization	(273)
Operating lease right-of-use assets, net	939
Total lease assets	45,475
Finance lease liabilities	12,071	0
Operating lease liabilities	591
Finance lease liabilities	43,780	$ 0
Operating lease liabilities	346
Total lease liabilities	$ 56,788

Leases - Components of Lease Ex

Leases - Components of Lease Expense (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018
Finance lease cost:
Amortization of right-of-use assets	$ 2,571	$ 5,140	$ 0
Interest on lease liabilities	609	1,249
Operating lease cost	163	289
Sublease income	(237)	(824)
Total lease cost	$ 3,106	$ 5,854

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information Related to Leases (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 191
Operating cash flows from finance leases	1,053
Financing cash flows from finance leases	5,850	$ 0
Right-of-use assets obtained in exchange for new lease liabilities:
Finance leases	49,676
Operating leases	$ 1,212

Leases - Schedule of Lease Term

Leases - Schedule of Lease Term and Discount Rate (Detail)	Jun. 30, 2019
Weighted-average remaining lease term (years):
Finance leases	4 years 1 month 6 days
Operating leases	1 year 4 months 24 days
Weighted-average discount rate:
Finance leases	4.43%
Operating leases	4.74%

Leases - Schedule of Maturities

Leases - Schedule of Maturities of Lease Liabilities (Detail) $ in Thousands	Jun. 30, 2019USD ($)
Finance Leases
2019 (Remaining six month period)	$ 7,002
2020	14,089
2021	13,678
2022	13,878
2023	12,523
Total future lease payments	61,170
Less: Interest	(5,319)
Present value of lease liabilities	55,851
Operating Leases
2019 (Remaining six month period)	313
2020	507
2021	134
2022	19
2023	0
Total future lease payments	973
Less: Interest	(36)
Present value of lease liabilities	$ 937

Leases - Schedule of Future Min

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

Leases - Schedule of Future M_2

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

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Cash And Cash Equivalents [Abstract]
Cash	$ 40,783	$ 38,783
US treasury notes and bills	0	49,934
Money market funds	33,804	541
Total cash and cash equivalents	$ 74,587	$ 89,258

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2019USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2019USD ($)Milestone	Jun. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents	$ 74,587,000		$ 74,587,000		$ 89,258,000
Contractual maturities of available-for-sale investments			1 year
Other-than-temporary impairment loss	0	$ 0	$ 0	$ 0
Provision to write-down excess and obsolete inventory	0		$ 0
Number of regulatory milestones | Milestone			2
Unbilled contract assets	180,000,000		$ 180,000,000		0
Building shell cost	140,786,000		140,786,000		192,397,000
Accumulated depreciation	95,921,000		95,921,000		65,199,000
Building shell [Member]
Schedule of Available-for-sale Securities [Line Items]
Building shell cost	0		0		53,880,000
Building [Member] | Build to suit arrangements [Member]
Schedule of Available-for-sale Securities [Line Items]
Accumulated depreciation					13,500,000
Leasehold improvements [Member]
Schedule of Available-for-sale Securities [Line Items]
Building shell cost	101,250,000		101,250,000		101,200,000
Leasehold improvements [Member] | Accounting standards update 2016-02 [Member]
Schedule of Available-for-sale Securities [Line Items]
Accumulated depreciation	38,900,000		38,900,000
Europe [Member]
Schedule of Available-for-sale Securities [Line Items]
Unbilled contract assets	130,000,000		130,000,000
Astellas Agreement [Member] | Europe [Member]
Schedule of Available-for-sale Securities [Line Items]
Unbilled contract assets	130,000,000		130,000,000
AstraZeneca Agreements [Member]
Schedule of Available-for-sale Securities [Line Items]
Unbilled contract assets	50,000,000		50,000,000
AstraZeneca Agreements [Member] | U.S./RoW [Member]
Schedule of Available-for-sale Securities [Line Items]
Unbilled contract assets	50,000,000		50,000,000
Foreign subsidiaries [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash and cash equivalents	$ 26,000,000		$ 26,000,000		$ 21,900,000

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Available-for-Sale Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 595,853	$ 587,885
Gross Unrealized Holding Gains	1,236	238
Gross Unrealized Holding Losses	0	(159)
Fair Value	597,089	587,964
US treasury notes and bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	475,126	467,296
Gross Unrealized Holding Gains	1,028	109
Gross Unrealized Holding Losses	0	(69)
Fair Value	476,154	467,336
Term deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	80,000	80,000
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Fair Value	80,000	80,000
Certificate of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	30,000	30,000
Gross Unrealized Holding Gains	21	0
Gross Unrealized Holding Losses	0	(90)
Fair Value	30,021	29,910
Bond and mutual funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,602	10,464
Gross Unrealized Holding Gains	75	20
Gross Unrealized Holding Losses	0	0
Fair Value	10,677	10,484
Equity investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	125	125
Gross Unrealized Holding Gains	112	109
Gross Unrealized Holding Losses	0	0
Fair Value	$ 237	$ 234

Balance Sheet Components - Sc_2

Balance Sheet Components - Schedule of Inventory (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Investments Schedule [Abstract]
Raw materials	$ 797
Work-in-progress	1,035
Finished goods	149
Total inventories	$ 1,981	$ 0

Balance Sheet Components - Sc_3

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Prepaid Expense And Other Assets Current [Abstract]
Unbilled contract assets	$ 180,000	$ 0
Deferred revenues from associated contracts	(52,019)	0
Net unbilled contract assets	127,981	0
Prepaid assets	4,716	2,705
Other current assets	3,899	2,224
Total prepaid expenses and other current assets	$ 136,596	$ 4,929

Balance Sheet Components - Sc_4

Balance Sheet Components - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 140,786	$ 192,397
Less: accumulated depreciation	(95,921)	(65,199)
Property and equipment, net	44,865	127,198
Leasehold improvements [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	101,250	101,200
Building shell [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	0	53,880
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	16,754	16,405
Machinery [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	8,461	8,382
Computer Equipment [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	6,655	6,473
Furniture and Fixtures [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	5,778	5,690
Construction in progress [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 1,888	$ 367

Balance Sheet Components - Sc_5

Balance Sheet Components - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Accrued Liabilities Current [Abstract]
Preclinical and clinical trial accruals	$ 41,104	$ 35,413
Payroll and related accruals	14,001	21,430
Property taxes and other	1,778	1,095
Professional services	3,588	2,648
Other	6,074	5,537
Total accrued liabilities	$ 66,545	$ 66,123

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Allocated Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 17,642	$ 13,231	$ 34,072	$ 24,109
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	10,450	7,894	20,028	14,264
Selling, general and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 7,192	$ 5,337	$ 14,044	$ 9,845

Stock-Based Compensation - Sc_2

Stock-Based Compensation - Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Purchases under 2014 Employee Share Purchase Plan (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Employee stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 3 months 18 days	5 years 4 months 24 days	5 years 3 months 18 days	5 years 4 months 24 days
Expected volatility	68.20%	67.50%	67.90%	67.80%
Risk-free interest rate	2.00%	2.80%	2.50%	2.70%
Expected dividend yield			0.00%	0.00%
Weighted average estimated fair value	$ 24.40	$ 31.35	$ 33.20	$ 32.12
2014 Employee Share Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	48.10%	47.30%	48.10%	47.30%
Expected volatility, maximum	62.10%	75.30%	62.10%	75.30%
Risk-free interest rate, minimum	1.30%	0.80%	1.30%	0.80%
Risk-free interest rate, maximum	2.90%	2.60%	2.90%	2.60%
Expected dividend yield			0.00%	0.00%
Weighted average estimated fair value	$ 19.07	$ 15.25	$ 19.65	$ 13.67
2014 Employee Share Purchase Plan [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 months	6 months	6 months	6 months
2014 Employee Share Purchase Plan [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	2 years	2 years	2 years	2 years

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Related Party Transaction [Line Items]
Accounts receivable from related party	$ 4,311,000		$ 4,311,000		$ 47,210,000
Accrued liabilities to related party	781,000		781,000		444,000
Unbilled contract asset	180,000,000		180,000,000		0
Due from Related Parties, Current	127,981,000		127,981,000		0
Net unbilled contract asset	127,981,000		127,981,000		0
Deferred Revenue	52,019,000		52,019,000		0
Europe [Member]
Related Party Transaction [Line Items]
Unbilled contract asset	130,000,000		130,000,000
Astellas Agreement [Member] | Europe [Member]
Related Party Transaction [Line Items]
Unbilled contract asset	130,000,000		130,000,000
Deferred Revenue	2,019,000		2,019,000
Astellas [Member] | Europe [Member]
Related Party Transaction [Line Items]
Unbilled contract asset	130,000,000		130,000,000
Net unbilled contract asset	128,000,000		128,000,000
Deferred Revenue	2,000,000		2,000,000
Astellas [Member] | Collaborative Arrangement [Member]
Related Party Transaction [Line Items]
Revenue related to collaboration agreements	134,700,000	$ 20,500,000	139,600,000	$ 25,600,000
Expense related to collaboration agreements	800,000	$ 200,000	1,300,000	$ 700,000
Accounts receivable from related party	4,300,000		4,300,000		47,200,000
Accrued liabilities to related party	$ 800,000		$ 800,000		400,000
Astellas [Member] | Astellas Agreement [Member] | API Shipment [Member]
Related Party Transaction [Line Items]
Accrued liabilities to related party					$ 43,800,000