Juno Therapeutics 10-K 29 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 18, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	JUNO
Entity Registrant Name	Juno Therapeutics, Inc.
Entity Central Index Key	1,594,864
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		104,059,558
Entity Public Float			$ 2,833,756,799

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 252,398	$ 355,968
Marketable securities	691,013	79,672
Prepaid expenses and other current assets	8,428	3,595
Total current assets	951,839	439,235
Property and equipment, net	42,086	4,018
Long-term marketable securities	272,888	38,411
Goodwill	122,092
Intangible assets	50,177
Other assets	6,046	7,499
Total assets	1,445,128	489,163
Current liabilities:
Accounts payable	4,248	1,096
Accrued liabilities and other current liabilities	33,376	14,577
Success payment liabilities	64,829	84,920
Contingent consideration	1,905
Deferred revenue	15,370
Total current liabilities	119,728	100,593
Build-to-suit lease obligation, less current portion	9,294
Contingent consideration obligations, less current portion	35,361
Deferred revenue, less current portion	129,831
Deferred tax liabilities	8,946
Other long-term liabilities	$ 435	$ 38
Commitments and contingencies (Note 14)
Stockholders' equity:
Preferred stock, $0.0001 par value; 5,000,000 shares authorized at December 31, 2015 and December 31, 2014; 0 shares issued and outstanding at December 31, 2015 and December 31, 2014
Common stock, $0.0001 par value, 495,000,000 shares authorized at December 31, 2015 and December 31, 2014; 97,247,058 and 82,073,647 shares issued and outstanding at December 31, 2015 and December 31, 2014, respectively	$ 10	$ 8
Additional paid-in-capital	1,733,263	734,895
Accumulated other comprehensive loss	(6,083)	(90)
Accumulated deficit	(585,657)	(346,281)
Total stockholders' equity	1,141,533	388,532
Total liabilities and stockholders' equity	$ 1,445,128	$ 489,163

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	495,000,000	495,000,000
Common stock, shares issued	97,247,058	82,073,647
Common stock, shares outstanding	97,247,058	82,073,647

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	5 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Revenue		$ 18,215
Operating expenses:
Research and development	$ 46,245	205,160	$ 204,511
General and administrative	4,238	51,130	19,529
Litigation	1,195	6,025	8,718
Total operating expenses	51,678	262,315	232,758
Loss from operations	(51,678)	(244,100)	(232,758)
Interest income, net		1,730	69
Other income (expenses), net	(142)	234	(10,718)
Loss before income taxes	(51,820)	(242,136)	(243,407)
Benefit for income taxes		2,760
Net loss	(51,820)	(239,376)	(243,407)
Net loss attributable to common stockholders:
Net loss	(51,820)	(239,376)	(243,407)
Deemed dividend upon issuance of convertible preferred stock, non-cash			(67,464)
Net loss attributable to common stockholders	$ (51,820)	$ (239,376)	$ (310,871)
Net loss per share attributable to common stockholders, basic and diluted	$ (14.16)	$ (2.72)	$ (36.82)
Weighted average common shares outstanding, basic and diluted	3,658,687	88,145,424	8,442,947

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	5 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net loss	$ (51,820)	$ (239,376)	$ (243,407)
Other comprehensive loss:
Unrealized loss on marketable securities		(5,388)	(90)
Foreign currency translation		(605)
Total other comprehensive loss		(5,993)	(90)
Comprehensive loss	$ (51,820)	$ (245,369)	$ (243,497)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	5 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
OPERATING ACTIVITIES
Net loss	$ (51,820)	$ (239,376)	$ (243,407)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	2	6,041	395
Stock-based compensation	125	31,941	6,504
Non-cash expense in connection with equity issuance	10,235		64,086
Loss from remeasurement of fair value of convertible preferred stock options	142		10,718
Deferred income taxes		(1,660)
Deferred tax benefit recorded in connection with acquisition		(1,100)
Change in fair value of success payment liabilities		51,557	84,920
Change in fair value of contingent consideration obligation		78
Gain on initial investment in Stage		(227)
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(258)	(6,855)	(7,380)
Accounts payable, accrued liabilities and other liabilities	11,064	22,144	1,619
Deferred revenue		144,782
Net cash provided by (used in) operating activities	(30,510)	7,325	(82,545)
INVESTING ACTIVITIES
Purchases of marketable securities		(1,315,597)	(118,372)
Sales and maturities of marketable securities		459,381
Acquisitions, net of cash acquired		(77,666)
Purchase of cost-method investment			(3,455)
Purchase of property and equipment	(42)	(28,184)	(2,958)
Net cash used in investing activities	(42)	(962,066)	(124,785)
FINANCING ACTIVITIES
Proceeds from issuance of common stock, net of (payments) of issuance costs	12	(1,683)	281,383
Proceeds from issuance of convertible preferred stock	66,506		245,949
Proceeds from issuance of common stock to strategic partner		849,804
Proceeds from exercise of stock options		3,366
Payments of build-to-suit lease obligation		(249)
Net cash provided by financing activities	66,518	851,238	527,332
Effect of exchange rate changes on cash and cash equivalents		(67)
Net (decrease) increase in cash and cash equivalents	35,966	(103,570)	320,002
Cash and cash equivalents at beginning of period		355,968	35,966
Cash and cash equivalents at end of period	35,966	252,398	355,968
SUPPLEMENTAL CASH FLOW INFORMATION
Purchases of property and equipment included in accounts payable and accrued liabilities		1,900	1,216
Amounts capitalized under build-to-suit leases		9,910
Issuance of common stock for acquisitions		41,611
Issuance of common stock for success payments		$ 71,648
Fair value of convertible preferred stock option at issuance	$ (3,971)		(6,889)
Deferred offering costs incurred but unpaid			$ 1,683

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Series A Preferred Stock [Member]	Series A-2 Preferred Stock [Member]	Series B Preferred Stock [Member]	Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member]Series A Preferred Stock [Member]	Convertible Preferred Stock [Member]Series A-2 Preferred Stock [Member]	Convertible Preferred Stock [Member]Series B Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]Series A Preferred Stock [Member]	Additional Paid-in Capital [Member]Series A-2 Preferred Stock [Member]	Additional Paid-in Capital [Member]Series B Preferred Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]	Accumulated Deficit [Member]Series A Preferred Stock [Member]	Accumulated Deficit [Member]Series A-2 Preferred Stock [Member]
Beginning balance at Dec. 31, 2013	$ (43,682)				$ 72,583				$ 1	$ 8,137					$ (51,820)
Conversion of preferred stock into common stock	387,695				$ (387,695)				$ 6	387,689
Issuance of stock			$ (212)	$ (1,487)		$ 20,000	$ 93,936	$ 133,712				$ (212)	$ (1,487)
Beginning balance, shares at Dec. 31, 2013					19,180,664				6,379,270
Conversion of preferred stock into common stock, shares					(59,909,397)				59,909,397
Issuance of stock, shares						5,000,000	23,484,072	12,244,661
Issuance of common stock	279,700								$ 1	279,699
Issuance of common stock, shares									12,676,354
Fair value of convertible preferred stock option at issuance	6,889		6,889									$ 6,889
Deemed dividends on issuance of convertible preferred stock, non-cash		$ (21,813)	$ (45,651)			$ 21,813	$ 45,651				$ (16,410)					$ (5,403)	$ (45,651)
Issuance of common stock to strategic partner, non-cash	64,086									64,086
Issuance of common stock to strategic partner, non-cash, shares									1,602,564
Stock-based compensation expense	6,504									6,504
Stock-based compensation expense, shares									1,506,062
Other comprehensive loss, net	(90)													$ (90)
Net loss	(243,407)														(243,407)
Ending balance at Dec. 31, 2014	388,532								$ 8	734,895				(90)	(346,281)
Ending balance, shares at Dec. 31, 2014									82,073,647
Issuance of stock as part of acquisition, non-cash	41,611									41,611
Issuance of stock as part of acquisition, non-cash, shares									852,713
Issuance of common stock to strategic partner, non-cash	849,804								$ 1	849,803
Issuance of common stock to strategic partner, non-cash, shares									9,137,672
Issuance of common stock for success payments	71,648									71,648
Issuance of common stock for success payments, shares									1,601,085
Issuance of common stock in connection with the Company's equity award programs	3,366									3,366
Issuance of common stock in connection with the Company's equity award programs, shares									3,581,941
Stock-based compensation expense	31,941								$ 1	31,940
Other comprehensive loss, net	(5,993)													(5,993)
Net loss	(239,376)														(239,376)
Ending balance at Dec. 31, 2015	$ 1,141,533								$ 10	$ 1,733,263				$ (6,083)	$ (585,657)
Ending balance, shares at Dec. 31, 2015									97,247,058

Consolidated Statements of Con8

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	5 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014
Common Stock [Member]
Issuance/Offering costs		$ 24,533
Series A Preferred Stock [Member] | Convertible Preferred Stock [Member]
Issuance/Offering costs	$ 289
Series A-2 Preferred Stock [Member] | Convertible Preferred Stock [Member]
Issuance/Offering costs		212
Series B Preferred Stock [Member] | Convertible Preferred Stock [Member]
Issuance/Offering costs		$ 1,487

Organization

Organization	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	1. Organization Juno Therapeutics, Inc. (the “Company”) was incorporated in Delaware on August 5, 2013 as FC Therapeutics, Inc., and changed its name to Juno Therapeutics, Inc. on October 23, 2013. The Company is building a fully-integrated biopharmaceutical company focused on re-engaging the body’s immune system to revolutionize the treatment of cancer. Founded on the vision that the use of human cells as therapeutic entities will drive one of the next important phases in medicine, the Company is developing cell-based cancer immunotherapies based on its chimeric antigen receptor (“CAR”) and high-affinity T cell receptor (“TCR”) technologies to genetically engineer T cells to recognize and kill cancer cells. In May 2015, the Company acquired all the remaining ownership interests in Stage Cell Therapeutics GmbH (“Stage”) not already held by it. See Note 3, Acquisitions. As a result of the acquisition, Stage has become a wholly owned subsidiary of the Company and the results of Stage have been consolidated with the Company’s results since the date of the acquisition. Stage has operations in Göttingen and Munich, Germany and its operations are focused on developing technology platforms, including novel reagents and automation technologies that enable the development and production of cell therapeutics. Stage has been renamed as Juno Therapeutics GmbH (“Juno GmbH”). In June 2015, the Company acquired X-Body, Inc. (“X-Body”). See Note 3, Acquisitions. As a result of the acquisition, X-Body has become a wholly owned subsidiary of the Company and the results of X-Body have been consolidated with the Company’s results since the date of the acquisition. X-Body has operations in Waltham, Massachusetts and its operations are focused on the discovery of human monoclonal antibodies and discovery of TCR binding domains. The Company is subject to a number of risks similar to other biopharmaceutical companies in the early stage, including, but not limited to, possible failure of preclinical testing or clinical trials, the need to obtain marketing approval for its product candidates, competitors developing new technological innovations, the need to successfully commercialize and gain market acceptance of the Company’s products, protection of proprietary technology, and the need to obtain adequate additional funding. If the Company, or any commercialization partner for the Company’s product candidates, does not successfully commercialize any of the Company’s product candidates, the Company will not be able to generate product revenue or achieve profitability. As of December 31, 2015, the Company had an accumulated deficit of $585.7 million.

Significant Accounting Policies

Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Significant Accounting Policies	2. Significant Accounting Policies Basis of Presentation and Use of Estimates The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The consolidated financial statements include the accounts of Juno Therapeutics, Inc. and its wholly-owned subsidiaries. All significant intercompany transactions and balances are eliminated in consolidation. The preparation of the Company’s consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from such estimates. The Company utilizes significant estimates and assumptions in determining the estimated success payment and contingent consideration liabilities and associated expense at each balance sheet date. A small change in the Company’s stock price may have a relatively large change in the estimated fair value of the success payment liability and associated expense. Changes in the probabilities and estimated timing of milestones used in the calculation of the contingent consideration liability may have a relatively large impact of the resulting liability and associated expense. Prior to becoming a public company, the Company utilized significant estimates and assumptions in determining the fair value of its common stock for financial reporting purposes. The Company recorded expense for restricted stock grants at prices not less than the fair market value of its common stock as determined by the board of directors, taking into consideration input from management and independent third-party valuation analysis, and in accordance with the AICPA Accounting and Valuation Guide, Valuation of Privately-Held Company Equity Securities Issued as Compensation. The estimated fair value of the Company’s common stock was based on a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector and the prices at which the Company sold shares of convertible preferred stock, and the superior rights and preferences of securities senior to the Company’s common stock at the time. Initial Public Offering On December 23, 2014, the Company closed its initial public offering (“IPO”) and issued and sold 12,676,354 shares of common stock (inclusive of 1,653,437 shares of common stock sold by the Company pursuant to the full exercise of the underwriters’ option to purchase additional shares) at a price to the public of $24.00 per share. The shares began trading on The NASDAQ Global Select Market on December 19, 2014. The aggregate net proceeds received by the Company from the offering, net of underwriting discounts and commissions and offering expenses, were $279.7 million. Upon the closing of the IPO, all then-outstanding shares of Company convertible preferred stock converted into 59,909,397 shares of common stock. The related carrying value of $387.7 million was reclassified to common stock and additional paid-in capital. Additionally, the Company amended and restated its certificate of incorporation effective December 23, 2014 to, among other things, change the authorized number of shares of common stock to 495,000,000 shares and the authorized number of shares of preferred stock to 5,000,000 shares. Comprehensive Loss Comprehensive loss is comprised of net loss and other comprehensive income or loss. Other comprehensive income or loss consists of unrealized gains and losses on marketable securities and foreign currency translation adjustments. Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less at acquisition to be cash equivalents. Cash equivalents, which consist primarily of money market funds, are stated at fair value. Marketable Securities The Company generally invests its excess cash in investment grade short- to intermediate-term fixed income securities. Such investments are included in cash and cash equivalents, marketable securities, or long-term marketable securities on the balance sheets, classified as available-for-sale, and reported at fair value with unrealized gains and losses included in accumulated other comprehensive income (loss). Realized gains and losses on the sale of these securities are recognized in net income or loss. The cost of marketable securities sold is based on the specific identification method. The Company periodically evaluates whether declines in fair values of its investments below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the investment until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any investment before recovery of its amortized cost basis. Factors considered include quoted market prices, recent financial results and operating trends, implied values from any recent transactions or offers of investee securities, credit quality of debt instrument issuers, other publicly available information that may affect the value of the investments, duration and severity of the decline in value, and our strategy and intentions for holding the investment. Property and Equipment, Net Property and equipment primarily consists of laboratory equipment, computer equipment and software, leasehold improvements and build-to-suit property. Property and equipment is stated at cost, and depreciated using the straight-line method over the estimated useful lives of the respective assets. Laboratory equipment 5 years Computer equipment and software 3 years Leasehold improvements Shorter of asset’s useful life or remaining term of lease Build-to-Suit Lease Accounting In February 2015, the Company entered into a lease for a manufacturing facility, which commenced in March 2015. The Company is responsible for the leasehold improvements required to remodel the facility and it bore the majority of the construction risk. Financial Accounting Standards Board (“FASB”) Accounting Standard Codification (“ASC”) 840-40, Leases—Sale-Leaseback Transactions (Subsection 05-5) Construction was completed in the first quarter of 2016, and the Company considered the requirements for sale-leaseback accounting treatment, including evaluating whether all risks of ownership have transferred back to the landlord, as evidenced by a lack of continuing involvement in the leased property. The Company determined that the arrangement does not qualify for sale-leaseback accounting treatment and the building asset will remain on its balance sheet at its historical cost, and such asset will be depreciated over its estimated useful life. The Company bifurcates the lease payments into a portion allocated to the building and a portion allocated to the parcel of land on which the building has been built. The portion of the lease payments allocated to the land is treated for accounting purposes as operating lease payments, and therefore is recorded as rent expense in the statements of operations. The portion of the lease payments allocated to the building is further bifurcated into a portion allocated to interest expense and a portion allocated to reduce the build-to-suit lease obligation. The interest rate used for the build-to-suit lease obligation represents the Company’s estimated incremental borrowing rate, adjusted to reduce any built in loss. Other Assets Prior to the acquisition of Stage in May 2015, the Company accounted for its minority interest investment in Stage using the cost method in accordance with ASC 325-20, Cost Method Investments Impairment of Long-Lived Assets The Company regularly reviews the carrying value and estimated lives of its long-lived assets, including property and equipment, to determine whether indicators of impairment may exist which warrant adjustments to carrying values or estimated useful lives. The determinants used for this evaluation include management’s estimate of the asset’s ability to generate positive income from operations and positive cash flow in future periods as well as the strategic significance of the asset to the Company’s business objectives. Should an impairment exist, the impairment loss would be measured based on the excess of the asset’s carrying amount over its fair value. The Company has not recognized any impairment losses since inception on August 5, 2013. Goodwill and Intangible Assets Goodwill represents the excess of the purchase price over the net amount of identifiable assets acquired and liabilities assumed in a business combination measured at fair value. The Company evaluates goodwill for impairment annually during the fourth quarter and upon the occurrence of triggering events or substantive changes in circumstances that could indicate a potential impairment by assessing qualitative factors or performing a quantitative analysis in determining whether it is more likely than not that the fair value of the net assets are below their carrying amounts. Intangible assets acquired in a business combination are recognized separately from goodwill and are initially recognized at their fair value at the acquisition date (which is regarded as their cost). Intangible assets related to in-process research and development (“IPR&D”) are treated as indefinite-lived intangible assets and not amortized until they become definite lived assets upon certain regulatory approval in specified markets, typically either the U.S. or the EU in the case of X-Body, and in the case of Stage, when the acquired reagents or automation technology is accepted by the FDA as part of an Investigational New Drug (“IND”) filing, subject to management judgment. At that time, the Company will determine the useful life of the asset, reclassify the asset out of IPR&D and begin amortization. Intangible assets are reviewed for impairment at least annually or if indicators of potential impairment exist. Contingent Consideration from Business Combinations At and subsequent to the acquisition date of a business combination, contingent consideration obligations are remeasured to fair value at each balance sheet date with changes in fair value recognized in research and development expense in the consolidated statements of operations. Changes in fair values reflect changes to the Company’s assumptions regarding probabilities of successful achievement of related milestones, the timing in which the milestones are expected to be achieved, and the discount rate used to estimate the fair value of the obligation, as well as the foreign currency impact of the contingent consideration for the Stage acquisition as it is denominated in Euro. Fair Value of Financial Instruments The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs: Level 1—Quoted prices in active markets for identical assets or liabilities Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly Level 3—Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability The Company’s financial instruments, in addition to those presented in Note 6, Fair Value Measurements, include cash and cash equivalents, accounts payable, and accrued liabilities. The carrying amount of cash and cash equivalents, accounts payable and accrued liabilities approximate fair value because of the short-term nature of these instruments. Convertible Preferred Stock Option Pursuant to certain 2013 and 2014 convertible preferred stock purchase agreements, the Company had the right to sell, or “put,” additional shares of Series A and A-2 convertible preferred stock in subsequent closings as well as potential obligations to issue additional shares upon the occurrence of certain events. The Company assessed its rights and potential obligations to sell additional shares and determined them to be a single unit of accounting, with classification outside of equity in accordance with ASC 480, Distinguishing Liabilities from Equity The Company recorded these combined instruments as convertible preferred stock options as of the date of the initial closings of the Series A convertible preferred stock financing and Series A-2 convertible preferred stock financing. The options were revalued to fair value at each subsequent balance sheet date, with fair value changes recognized as increases or reductions to other income (expense), net in the consolidated statements of operations. The Company estimated the fair value of these instruments based on the Black-Scholes option pricing model. These options were exercised during 2014. For the year ended December 31, 2014, $10.7 million was recognized in other expense related to the changes in fair value of these options. Deemed Dividends upon Issuance of Convertible Preferred Stock, Non-Cash As of the dates of the second tranche closing and third tranche closing of the Series A-2 convertible preferred stock financing in June and July 2014, the estimated fair value of the Series A-2 convertible preferred stock was $5.96 and $7.88 per share, respectively, compared with the purchase price per share of $4.00. As of the date of the final closing of the Series A convertible preferred stock financing in July 2014, the estimated fair value of the Series A convertible preferred stock was $8.36 per share compared with the purchase price per share of $4.00. The differences between the estimated fair value as of the closing dates and the purchase prices were deemed to be equivalent to a preferred stock dividend. As a result, the Company recorded deemed dividends of $15.4 million, $30.3 million, and $21.8 million for the Series A-2 second tranche closing, Series A-2 third tranche closing, and Series A final closing, respectively, in the year ended December 31, 2014. The deemed dividends increased convertible preferred stock by $67.5 million, reduced additional paid-in capital by $16.4 million, and increased accumulated deficit by $51.1 million. The deemed dividends increased the net loss attributable to common stockholders by $67.5 million in the calculation of basic and diluted net loss per common share for the year ended December 31, 2014. Success Payments The Company granted rights to share-based success payments to the Fred Hutchinson Cancer Research Center (“FHCRC”) and the Memorial Sloan Kettering Cancer Center (“MSK”) pursuant to the terms of its collaboration agreements with each of those entities. Pursuant to the terms of these arrangements, the Company may be required to make success payments based on increases in the per share fair market value of the Company’s common stock, payable in cash or publicly-traded equity at the Company’s discretion. See Note 4, Collaboration and License Agreements. The success payments are accounted for under ASC 505-50, Equity-Based Payments to Non-Employees Derivatives and Hedging Success payment liabilities are estimated at fair value at inception and at each subsequent balance sheet date and the expense is amortized using the accelerated attribution method over the remaining term (service period) of the related collaboration agreement or related possible payment due date (whichever is sooner). To determine the estimated fair value of the success payments the Company uses a Monte Carlo simulation methodology which models the future movement of stock prices based on several key variables. The following variables were incorporated in the estimated fair value of the success payment liability: estimated term of the success payments, fair value of common stock, expected volatility, risk-free interest rate, estimated number and timing of valuation measurement dates on the basis of which payments may be triggered, and certain estimated indirect costs creditable against the success payments are also included in the calculation. The computation of expected volatility was estimated using a combination of available information about the historical volatility of stocks of similar publicly-traded companies for a period matching the expected term assumption and its historical and projected volatility. In addition, prior to the Company becoming publicly traded there was one valuation measurement date on the basis of which payments may be triggered. There are several valuation measurement dates subsequent to the IPO on the basis of which payments may be triggered. In December 2015, success payments to FHCRC were triggered in the aggregate amount of $75.0 million, less indirect cost offsets of $3.3 million. The Company elected to make the payment in shares of the Company’s common stock, and thereby issued 1,601,085 shares of common stock to FHCRC in December 2015. In December 2015, a success payment to MSK was triggered in the amount of $10.0 million, which is required to be paid, less indirect cost offsets that will be determined at the time of payment, in March 2016. As of December 31, 2015 and 2014, the estimated fair value of the success payment obligation after giving effect to the success payments achieved by FHCRC and MSK was approximately $116.2 million and $195.9 million, respectively. The Company recognized research and development expense of $51.6 million and $84.9 million in the year ended December 31, 2015 and 2014, respectively, with respect to the success payment obligations. The success payment liabilities on the consolidated balance sheets as of December 31, 2015 and 2014 were $64.8 million and $84.9 million, respectively. The assumptions used to calculate the fair value of the success payments are subject to a significant amount of judgment including the expected volatility, estimated term, and estimated number and timing of valuation measurement dates. A small change in the assumptions may have a relatively large change in the estimated valuation and associated liability and expense. For example, keeping all other variables constant, a hypothetical 10% increase in the stock price at December 31, 2015 from $43.97 per share to $48.37 per share would have increased the expense recorded in 2015 associated with the success payment liability by $7.7 million. A hypothetical 10% decrease in the stock price from $43.97 per share to $39.57 per share would have decreased the expense recorded in 2015 associated with the success payment liability by $7.6 million. Further, keeping all other variables constant, a hypothetical 35% increase in the stock price at December 31, 2015 from $43.97 per share to $59.36 per share would have increased the expense recorded in 2015 associated with the success payment liability by $27.3 million. A hypothetical 35% decrease in the stock price from $43.97 per share to $28.58 per share would have decreased the expense recorded in 2015 associated with the success payment liability by $25.7 million. Concentrations of Credit Risk and Off-Balance Sheet Risk The Company maintains its cash, cash equivalents, and marketable securities with high quality, accredited financial institutions. These amounts at times may exceed federally insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to significant risk on these funds. The Company has no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements. Revenue The Company recognizes revenue for each unit of accounting when all of the following criteria are met: • persuasive evidence of an arrangement exists; • delivery has occurred or services have been rendered; • the seller’s price to the buyer is fixed or determinable; and • collectability is reasonably assured. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue in current liabilities. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, less current portion. The Company analyzes agreements with more than one element, or deliverable, based on the guidance in ASC 605-25, Revenue Recognition-Multiple-Element Arrangements (“ASC 605-25”). The Company identifies the deliverables within the agreement and evaluates which deliverables represent separate units of accounting. Analyzing the agreement to identify deliverables requires the use of judgment. A deliverable is considered a separate unit of accounting when the deliverable has value to the collaborator or licensee on a standalone basis based on the consideration of the relevant facts and circumstances for each agreement. In assessing whether an item has standalone value, the Company considers factors such as the research, manufacturing, and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the other deliverable(s) can be used for their intended purpose without the receipt of the remaining element(s), whether the value of the deliverable is dependent on the undelivered item(s) and whether there are other vendors that can provide the undelivered element(s). Consideration received is allocated at the inception of the agreement to all identified units of accounting based on the relative selling prices. The relative selling price for each deliverable is estimated using objective evidence if it is available. If objective evidence is not available, the Company uses its best estimate of the selling price for the deliverable. Management may be required to exercise considerable judgment in estimating the selling prices of identified units of accounting under its agreements. Options for future deliverables are considered substantive if, at the inception of the arrangement, the Company is at risk as to whether the collaboration partner will choose to exercise the option. Factors that the Company considers in evaluating whether an option is substantive include the overall objective of the arrangement, the benefit the collaborator might obtain from the arrangement without exercising the option, the cost to exercise the option and the likelihood that the option will be exercised. For arrangements under which an option is considered substantive, the Company does not consider the item underlying the option to be a deliverable at the inception of the arrangement and the associated option fees are not included in the initial consideration, assuming the option is not priced at a significant and incremental discount. Conversely, for arrangements under which an option is not considered substantive or if an option is priced at a significant and incremental discount, the Company would consider the item underlying the option to be a deliverable at the inception of the arrangement and a corresponding amount would be included in the initial consideration. The consideration received is allocated among the separate units of accounting, and the applicable revenue recognition criteria are applied to each of the separate units. The Company recognizes the revenue allocated to each unit of accounting over the period of performance. Revenue is recognized using either a proportional performance or straight-line method, depending on whether the Company can reasonably estimate the level of effort required to complete its performance obligations under an arrangement. Research and Development Expense The Company records expense for research and development costs to operations as incurred. For service contracts entered into that include a nonrefundable prepayment for service, the upfront payment is deferred and recognized in the statement of operations as the services are rendered. Research and development expenses consist of costs incurred by the Company for the discovery and development of the Company’s product candidates and include: • Clinical trial costs; • external research and development expenses incurred under arrangements with third parties, such as contract research organizations, contract manufacturing organizations, academic and non-profit institutions and consultants; • costs incurred in connection with preclinical development activities; • costs to acquire complimentary technology; • personnel-related expenses, including non-cash stock-based compensation expense; • changes in the estimated fair value of the liability attributable to the elapsed service period as of the balance sheet date associated with the Company’s success payments to FHCRC and MSK; • changes in the estimated fair value of the contingent consideration liabilities; • license fees; and • other expenses, which include direct and allocated expenses for laboratory, facilities, and other costs. General and Administrative Expense General and administrative costs are expensed as incurred and include personnel-related expenses including non-cash stock-based compensation for our personnel in executive, legal, finance and accounting, and other administrative functions, legal costs other than litigation expense associated with Trustees of the University of Pennsylvania v. St. Jude Children’s Research Hospital Litigation Expense Litigation expense includes legal expense the Company incurred with respect to Trustees of the University of Pennsylvania v. St. Jude Children’s Research Hospital Stock-Based Compensation Under ASC 718, Compensation—Stock Compensation, • the expected term of the option, which is calculated using the simplified method, as permitted by the Securities and Exchange Commission (“SEC”) Staff Accounting Bulletin No. 110, Share-Based Payment, as the Company has insufficient historical information regarding its stock options to provide a basis for an estimate; • the expected volatility of the underlying common stock, which the Company estimates based on the historical volatility of a representative group of publicly traded biopharmaceutical companies with similar characteristics, and the Company’s own historical and implied future volatility; • the risk-free interest rate, which is based on the yield curve of U.S. Treasury securities with periods commensurate with the expected term of the options being valued; • the expected dividend yield, which the Company estimates to be zero based on the fact that the Company has never paid cash dividends and has no present intention to pay cash dividends; and • the fair value of the Company’s common stock on the date of grant. Stock-based compensation expense for restricted stock, RSUs, and stock options is recognized on a straight-line basis over the requisite service period, which is generally the vesting period of the respective award. The Company is required to estimate a forfeiture rate to calculate the stock-based compensation expense for its awards. The Company’s forfeiture rate is based on an analysis of its actual forfeitures since the adoption of its equity award plan. Since inception the Company’s estimated forfeiture rate has been de minimis The Company also granted restricted stock awards that vest in conjunction with certain performance conditions to certain key employees, scientific founders, and directors. At each reporting date, the Company is required to evaluate whether achievement of the performance conditions is probable. Compensation expense is recorded over the appropriate service period based upon the Company’s assessment of accomplishing each performance provision. Compensation expense is measured using the fair value of the award at the grant date, net of forfeitures, and is adjusted annually to reflect actual forfeitures. The Company also grants stock-based awards to certain service providers who are not employees, scientific founders, or directors. Stock-based awards issued to such persons, or to directors for non-board related services, are accounted for based on the fair value of such services received or of the equity instruments issued, whichever is more reliably measured. The fair value of such awards is subject to remeasurement at each reporting period until services required under the arrangement are completed, which is the vesting date. Patent Costs The costs related to acquiring patents and to prosecuting and maintaining intellectual property rights are expensed as incurred to general and administrative due to the uncertainty surrounding the drug development process and the uncertainty of future benefits. Income Taxes The Company determines its deferred tax assets and liabilities based on the differences between the financial reporting and tax basis of assets and liabilities. The deferred tax assets and liabilities are measured using the enacted tax rates that will be in effect when the differences are expected to reverse. A valuation allowance is recorded when it is more likely than not that the deferred tax asset will not be recovered. The Company applies judgment in the determination of the consolidated financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The Company recognizes any material interest and penalties related to unrecognized tax benefits in income tax expense. The Company is required to file income tax returns in the U.S. federal jurisdiction and various state and foreign jurisdictions. The Company currently is not under examination by the Internal Revenue Service or other jurisdictions for any tax years. Foreign Currency Translation Assets and liabilities denominated in foreign currencies were translated into U.S. dollars, the reporting currency, at the exchange rate prevailing at the balance sheet date. Revenue and expenses denominated in foreign currencies were translated into U.S. dollars at the monthly average exchange rate for the period and the translation adjustments are reported as an element of accumulated other comprehensive income or loss on the consolidated balance sheets. Net Loss per Share Attributable to Common Stockholders Basic and diluted net loss per share attributable to common stockholders is calculated by dividing net loss attributable to common stockholders by the weighted average number of common shares outstanding during the period, without consideration for common stock equivalents. The Company’s potentially dilutive shares, which include unvested restricted stock, unvested RSUs, options to purchase common stock, and potential shares issued for success payments, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The following table reconciles net loss to net loss attributable to common stockholders (in thousands, except share and per share data): Year Ended December 31, Period from December 31, 2013 2015 2014 Net loss $ (239,376 ) $ (243,407 ) $ (51,820 ) Deemed dividend upon issuance of convertible preferred stock — (67,464 ) — Net loss attributable to common stockholders $ (239,376 ) $ (310,871 ) $ (51,820 ) Weighted average number of common shares used in net loss per share attributable to common stockholders—basic and diluted 88,145,424 8,442,947 3,658,687 Net loss per share attributable to common stockholders—basic and diluted $ (2.72 ) $ (36.82 ) $ (14.16 ) The amounts in the table below were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated due to their anti-dilutive effect: Year Ended December 31, Period from December 31, 2013 2015 2014 Series A convertible preferred stock — — 16,930,664 Series A-1 convertible preferred stock — — 2,250,000 Unvested restricted common stock and restricted stock units 5,476,600 8,352,714 5,789,123 Options to purchase common stock 5,218,939 2,720,351 — Estimated number of shares issued for success payments 204,527 1 1,627,729 2 — Total 10,900,066

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2015
Business Combinations [Abstract]
Acquisitions	3. Acquisitions Acquisition of Stage On May 11, 2015, the Company completed the acquisition of all the outstanding ownership interests in Stage not already held by it. Prior to the acquisition, the Company held a 4.76% equity interest in Stage. As a result of the acquisition, Stage became a wholly owned subsidiary of the Company. The Company paid €52.5 million, or $58.5 million, in cash and issued an aggregate of 486,279 shares of common stock, valued at $22.2 million based on the closing stock price on May 11, 2015 of $45.58 per share, to the selling shareholders. The Company also agreed to pay additional amounts of up to an aggregate of €135.0 million in cash based on the achievement of certain technical, clinical, regulatory, and commercial milestones related to novel reagents (€40.0 million), advanced automation technology (€65.0 million), and Stage’s existing clinical pipeline (€30.0 million). The fair value of this contingent consideration was estimated to be $28.2 million at the date of acquisition. Payments could vary based on milestones that are reached. The elements of the purchase consideration are as follows (in thousands): Cash paid (1) $ 58,496 Common stock issued (2) 22,165 Fair value of contingent consideration (3) 28,244 Total consideration for 95.24% equity 108,905 Fair value of 4.76% initial investment in Stage (4) 3,682 Implied purchase price consideration for 100% equity $ 112,587 (1) The cash consideration represents the consideration paid in cash amounting to €52.5 million which is translated based on an exchange rate on May 11, 2015. (2) Based on the share purchase agreement, the purchase consideration included 486,279 shares of the Company’s common stock. The closing stock price on the transaction date was $45.58 per share. (3) The fair value of the contingent consideration was determined by calculating the probability-weighted milestone payments based on the assessment of the likelihood and estimated timing that certain milestones would be achieved. The fair value of the contingent consideration was estimated using a discount rate of 14.6%. The discount rate captures the credit risk associated with the payment of the contingent consideration when earned and due. (4) The fair value of the initial investment is calculated as the implied per share fair value of the stock based upon the acquisition purchase price reduced by a lack of control discount associated with the 4.76% holding. Upon acquiring the remaining outstanding ownership interests in Stage, the Company remeasured its original equity interest to its fair value and recognized a $0.2 million gain during the year ended December 31, 2015, which was recorded in other income (expense) on the consolidated statements of operations. The Company accounted for the Stage acquisition using the acquisition method. The acquisition method of accounting requires, among other things, that the assets acquired and liabilities assumed in a business combination be measured at their fair values as of the closing date of the acquisition. The allocation of the purchase price is based on estimates of the fair value of assets acquired and liabilities assumed as of the date of acquisition. The components of the purchase price allocation are as follows (in thousands): Net working capital $ 1,863 Property and equipment 651 Net assets acquired 2,514 Deferred tax liabilities (10,801 ) Acquired in-process research and development 34,457 Goodwill 86,417 Total consideration transferred $ 112,587 The fair value of the acquired in-process research and development has been estimated using the replacement cost method. Under this method, the Company estimated the cost of recreating the technology and derived an estimated value to develop the technology. In-process research and development are required to be classified as indefinite-lived assets until they become definite lived assets upon the successful completion or the abandonment of the associated research and development effort. Accordingly, during the development period after the date of acquisition, these assets will not be amortized until the acquired reagents or automation technology is accepted by the FDA as part of an IND, subject to management judgment. At that time, the Company will determine the useful life of the asset and begin amortization. If the associated research and development effort is abandoned, the related in-process research and development assets will be written-off and an impairment charge recorded. The excess of the purchase price over the estimated fair value of the tangible net assets and identifiable intangible assets acquired was recorded as goodwill. The factors contributing to the recognition of the amount of goodwill are based on several strategic and synergistic benefits that are expected to be realized from the Stage acquisition. The acquisition of Stage is intended to provide the Company access to transformative cell selection and activation capabilities, next generation manufacturing automation technologies, enhanced control of its supply chain, and lower expected long-term cost of goods. None of the goodwill is expected to be deductible for income tax purposes. The Company made a Section 338(g) election under the Internal Revenue Code with respect to this acquisition, resulting in the acquired entity being treated for U.S. tax purposes as a newly incorporated company. Under such election, the U.S. tax basis of the assets and liabilities of Stage were stepped up to fair value as of the closing date of the acquisition to reflect the consequences of the Section 338(g) election. Acquisition of X-Body On June 1, 2015, the Company completed the acquisition of 100% of the outstanding equity in X-Body. The Company paid $21.3 million in cash and issued an aggregate of 366,434 shares of common stock, valued at $19.4 million based on the closing stock price on June 1, 2015 of $53.07 per share, to the former X-Body stockholders. Further, an additional 72,831 shares of common stock were issued to two former X-Body stockholders in the transaction, which shares are subject to monthly vesting over the three years following the closing of the transaction, contingent on such former X-Body stockholders providing consulting services to the Company through each such vesting date. These will be accounted for as post-acquisition compensation expenses. The Company also agreed to pay additional amounts in cash upon the realization of specified milestones substantially as follows, with respect to products generated using the X-Body technology: $5.0 million per target upon the achievement, during a specified period, of a certain regulatory milestone for products that utilize a certain type of binding mechanism; up to $30.0 million upon the achievement, during a specified period, of regulatory and clinical milestones for the first product using another type of binding mechanism (any product using such type of binding mechanism, a “Type X Product”); $5.0 million per product upon the achievement, during a specified period, of a certain regulatory milestone for a certain number of subsequent Type X Products; $50.0 million upon the achievement, during a specified period, of a clinical milestone related to the first product with certain specified binding properties (a “Type Y Product”); and $20.0 million upon the achievement, during a specified period, of a clinical milestone related to the first product with certain other specified binding properties. If a Type X Product or a Type Y Product is commercialized, Juno can choose either to make a commercialization milestone payment for such a product or to pay a low single-digit royalty on net sales of such a product. The fair value of this contingent consideration was estimated to be $8.9 million at the date of acquisition. Payments could vary based on milestones that are reached. The elements of the purchase consideration are as follows (in thousands): Cash paid $ 21,331 Common stock issued (1) 19,447 Fair value of contingent consideration (2) 8,944 Settlement of preexisting obligation (3) 1,123 Total consideration $ 50,845 (1) Based on the share purchase agreement, the purchase consideration included 366,434 shares of the Company’s common stock. The closing stock price on the transaction date was $53.07 per share. (2) The fair value of the contingent consideration was determined by calculating the probability-weighted milestone based on the assessment of the likelihood and estimated timing that certain milestones would be achieved. The fair value of the contingent consideration was estimated using a discount rate of 15.2%. The discount rate captures the credit risk associated with the payment of the contingent consideration when earned and due. (3) The settlement of preexisting obligation reflects the effective settlement of the Company’s preexisting prepaid contract research agreement with X-Body. No gain or loss was recognized by the Company on the effective settlement of this prepaid expense as of the acquisition date. The allocation of the purchase price is based on estimates of the fair value of assets acquired and liabilities assumed as of the acquisition date. The components of the purchase price allocation are as follows (in thousands): Net liabilities assumed $ (181 ) Deferred tax liabilities (1,099 ) Acquired in-process research and development 16,450 Goodwill 35,675 Total consideration transferred $ 50,845 The fair value of the acquired in-process research and development has been estimated using the replacement cost method. Under this method, the Company estimated the cost to recreate the technology and derived an estimated value to develop the technology. In-process research and development are required to be classified as indefinite-lived assets until they become definite lived assets upon the successful completion or the abandonment of the associated research and development effort. Accordingly, during the development period after the date of acquisition, these assets will not be amortized until regulatory approval is obtained in a major market, typically either the United States or the EU, subject to management judgment. At that time, the Company will determine the useful life of the asset and begin amortization. If the associated research and development effort is abandoned, the related in-process research and development assets will be written-off and an impairment charge recorded. The excess of the purchase price over the estimated fair value of the tangible net assets and identifiable intangible assets acquired was recorded as goodwill. The goodwill recognized as a result of the X-Body acquisition is primarily attributable to the fact that the acquisition furthers the Company’s strategy of investing in technologies that augment the Company’s capabilities to create best-in-class engineered T cells against a broad array of cancer targets. The acquisition brings in-house to the Company an innovative discovery platform that interrogates the human antibody repertoire, rapidly selecting fully human antibodies with desired characteristics, even against difficult targets. None of the goodwill is expected to be deductible for income tax purposes. Post-Acquisition and Pro Forma Consolidated Financial Information The Stage and X-Body acquisitions did not have a material impact on the Company’s consolidated statements of operations, and therefore actual and pro forma disclosures have not been presented. The intangible assets acquired in the Stage and X-Body acquisitions are in-process research and development assets, and as such, there would be no pro forma adjustment needed for the amortization of intangible assets. Goodwill and Intangible Assets The following table summarizes the changes in the carrying amount of goodwill (in thousands): Balance at December 31, 2014 $ — Goodwill acquired 122,092 Balance at December 31, 2015 $ 122,092 Goodwill represents the excess of the purchase price over the net amount of identifiable assets acquired and liabilities assumed in a business combination measured at fair value. We evaluate goodwill for impairment annually during the fourth quarter and upon the occurrence of triggering events or substantive changes in circumstances that could indicate a potential impairment by assessing qualitative factors or performing a quantitative analysis in determining whether it is more likely than not that the fair value of net assets are below their carrying amounts. There was no impairment of goodwill for the year ended December 31, 2015. The following table summarizes the gross carrying amount, accumulated amortization and the net carrying amount of intangible assets (in thousands): December 31, 2015 Gross Carrying Accumulated Intangible Acquired in-process research and development $ 50,177 $ — $ 50,177 Total intangible assets $ 50,177 $ — $ 50,177 Intangible assets acquired in a business combination are recognized separately from goodwill and are initially recognized at their fair value at the acquisition date (which is regarded as their cost). Intangible assets related to IPR&D are treated as indefinite-lived intangible assets and not amortized until they become definite lived assets upon obtaining certain regulatory approval in specified markets in the case of X-Body, and in the case of Stage, when the acquired reagents or automation technology is accepted by the FDA as part of an IND, subject to management judgment. At that time, the Company will determine the useful life of the asset, reclassify the asset out of IPR&D and begin amortization. Intangible assets are reviewed for impairment at least annually or if indicators of potential impairment exist. There was no impairment of intangible assets for the year ended December 31, 2015. Transaction Costs The Company incurred approximately $4.5 million of direct transaction costs related to the Stage and X-Body acquisitions for the year ended December 31, 2015. These costs are included in general and administrative expenses in the consolidated statements of operations.

Collaboration and License Agree

Collaboration and License Agreements	12 Months Ended
	Dec. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Collaboration and License Agreements	4. Collaboration and License Agreements Celgene In June 2015, the Company entered into a Master Research and Collaboration Agreement (“Celgene Collaboration Agreement”) with Celgene Corporation and one of its wholly owned subsidiaries (collectively, “Celgene”) pursuant to which the Company and Celgene agreed to collaborate on researching, developing, and commercializing novel cellular therapy product candidates and other immuno-oncology and immunology therapeutics, including, in particular, CAR and TCR product candidates. The Celgene Collaboration Agreement was amended and restated in August 2015. Pursuant to the collaboration, prior to the exercise of an option for a program, each of the Company and Celgene will conduct independent programs to research, develop, and commercialize such product candidates (including, in the case of the Company, its CD19 and CD22 programs). Each party has certain options to obtain either an exclusive license to develop and commercialize specified product candidates arising from specified types of programs conducted by the other party within the scope of the collaboration, or the right to participate in the co-development and co-commercialization of specified product candidates arising from such programs, in each case in specified territories. Further, following the exercise of an option, Celgene has the right to exercise an option for a specified number of such programs, excluding the CD19 program and the CD22 program, to co-develop and co-commercialize products arising out of such programs in certain countries, and each of Celgene and Company has the right to elect to participate in certain commercialization activities for products in such programs in territories where it is not leading commercialization of such product. The parties may exercise their options with respect to specified product candidates arising under programs within the scope of the collaboration until the tenth anniversary of the effective date of the Celgene Collaboration Agreement (the “Research Collaboration Term”), subject to a tail period applicable to certain programs, for which options have not yet been exercised as of the expiration of the Research Collaboration Term. For Company-originated programs (which may include the CD19 program and the CD22 program) under the collaboration for which Celgene exercises its option to obtain an exclusive license: • The Company would be responsible for research and development in the United States, Canada, and Mexico, and, for cellular therapy product candidates, China, and would retain commercialization rights and would lead commercialization activities and book sales of products in those countries (the “Juno Territory”), subject to Celgene’s option, for a specified number of programs, to elect to co-develop and co-commercialize product candidates arising from such programs, or for other programs, to elect to participate in certain commercialization activities in the Juno Territory, as further described below. Under all such license agreements, the Company has the right to participate in specified commercialization activities arising from such programs in certain major European markets; • On a program-by-program basis, Celgene would receive an exclusive license, and pursuant to such license would be responsible for, development and commercialization outside of the Juno Territory (the “Celgene Territory”), including by leading commercialization activities and booking sales of products in the Celgene Territory. Celgene would be required to pay the Company a royalty on sales of products arising from such program in the Celgene Territory as further described below; and • For Company-originated programs, excluding CD19 and CD22, Celgene would have the right to exercise an option for a specified number of such programs, to obtain the right to co-develop and co-commercialize products arising from such program worldwide, except for China. For each such program, following Celgene’s exercise of such option, the parties would enter into an agreed form of co-development and co-commercialization agreement, pursuant to which: • Celgene would have the right to co-develop and co-commercialize product candidates arising from such programs, with the parties each entitled to bear and receive an equal share of the profits and losses arising from development and commercialization activities in such programs worldwide (other than China); and • The Company would remain the lead party for development and commercialization activities for such product candidates in the Juno Territory, and Celgene would remain the lead party for development and commercialization activities for such product candidates in the Celgene Territory, subject to the Company’s right to participate in certain commercialization activities in certain major European countries, and Celgene’s right to elect to participate in a specified percentage of commercialization activities in the Juno Territory. For other Company originated programs for which Celgene does not exercise such a co-development and co-commercialization right, Celgene would also have the right to elect to participate in up to a specified percentage of certain commercialization activities for product candidates in such program in the Juno Territory, and the Company would have the right to elect to participate in up to a specified percentage of certain commercialization activities for such product candidates in certain major European markets. For Celgene-originated programs under the collaboration for which the Company exercises its option to obtain an exclusive license, the parties will enter into a co-development and co-commercialization agreement and: • The parties will share global profits and losses from development and commercialization activities with 70% allocated to Celgene and 30% allocated to the Company; and • Celgene will lead global development and commercialization activities, subject to the Company’s right to elect to participate in up to a specified percentage of certain commercialization activities in the Juno Territory under certain circumstances and in certain major European countries. Furthermore, each of Celgene and the Company will have the exclusive right to exercise options to co-develop and co-commercialize product candidates arising out of programs for which the other party in-licenses or acquires rights that are within the scope of their collaboration, where such rights are available to be granted, with the parties each bearing an equal share of the profits and losses arising out of such programs following the exercise of such option. In general, for such programs where the rights are in-licensed or acquired by the Company and for which Celgene exercises its options, the Company will be the lead party for development and commercialization of product candidates arising from such programs in the Juno Territory, subject to Celgene’s right to elect to participate in certain commercialization activities for such product candidates in the Juno Territory, and Celgene will be the lead party for development and commercialization of product candidates arising in such programs in the Celgene Territory, subject to the Company’s right to elect to participate in certain commercialization activities for such product candidates in certain major European markets. Conversely, for such programs where the rights are in-licensed or acquired by Celgene and for which the Company exercises its options, Celgene will be the lead party for development and commercialization activities for product candidates arising from such programs on a worldwide basis, subject to the Company’s right to elect to participate in certain commercialization activities for such product candidates in the Juno Territory and in certain major European markets. The party exercising an option for these in-licensed or acquired programs is generally required to pay to the other party an upfront payment equal to one half of the costs incurred by other party in connection with the acquisition of rights to such programs. In addition to an upfront cash payment of approximately $150.2 million under the Celgene Collaboration Agreement, Celgene is required to pay to the Company an additional fee if it exercises its option for each of the CD19 Program and the CD22 Program, totaling, if the options are exercised for both programs during the initial opt-in window, $100.0 million. Upon a party’s exercise of the option for any other program (other than certain in-licensed or acquired programs where a party exercises its option at the time such program is acquired), the party exercising the option is required to pay to the other party a payment at the time of exercise of its option, calculated as a multiple of the costs incurred by the other party in relation to the development activities for such program prior to the exercise of the option, with such multiple based on the point in development of such product at which such party exercises such option. For programs for which the parties have entered into a license agreement, the Company will also receive royalties from Celgene, for product candidates arising from the CD19 and CD22 programs, at a percentage in the mid-teens of net sales of such product candidates in the Celgene Territory, and for product candidates arising from other Company programs that are subject to a license agreement, tiered royalties on net sales of such product candidates in the Celgene Territory, at percentages ranging from the high single digits to the mid-teens, calculated based on the stage of development at which Celgene exercises its option for such program. In June 2015, the Company also entered into a Share Purchase Agreement (the “Purchase Agreement”) with Celgene. Pursuant to the Purchase Agreement, the Company agreed to sell 9,137,672 shares of the Company’s common stock to Celgene at an aggregate cash price of approximately $849.8 million, or $93.00 per share of common stock, at an initial closing (the “Initial Closing”). Beyond the Initial Closing, the Purchase Agreement provides for potential future sales of shares by the Company to Celgene as follows: • First Period Top-Up Rights. • First Acquisition Right. • Second Period Top-Up Rights. • Second Acquisition Right. • Final Top-Up Rights. The First Period Top-Up Rights, Second Period Top-Up Rights and Third Period Top-Up Rights are collectively referred to herein as the “Top-Up Rights”. The First Acquisition Right and Second Acquisition Right are collectively referred to herein as the “Acquisition Rights.” Each closing of the sale of shares to Celgene is subject to customary closing conditions, including termination or expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended. The Purchase Agreement also limits the aggregate number of shares that may be issued thereunder to 19.99% of the Company’s common stock outstanding immediately prior to the entry into the Purchase Agreement, unless stockholder approval is obtained for additional issuances of Company stock in accordance with NASDAQ rules. The Company has agreed to submit the additional equity issuances for approval by its stockholders at the Company’s 2016 annual meeting of stockholders. The Celgene Collaboration Agreement became effective on July 31, 2015, in connection with which the Company received an upfront cash payment of $150.2 million. On August 4, 2015 the Initial Closing under the Purchase Agreement occurred, and the Company sold 9,137,672 shares of the Company’s common stock to Celgene for an aggregate cash purchase price of approximately $849.8 million. Accounting Analysis The Celgene Collaboration Agreement contains the following deliverables: (1) access to certain of the Company’s technology through a non-exclusive, worldwide, royalty-free right and license to conduct certain activities under the collaboration, and (2) participation on various collaboration committees. The Company considered the provisions of the multiple-element arrangement guidance in determining how to recognize the revenue associated with the two deliverables. The Company has accounted for access to certain of the Company’s technology and participation on various collaboration committees as a single unit of accounting because the two deliverables do not have standalone value and both obligations will be delivered throughout the estimated period of performance. Under the terms of the Celgene Collaboration Agreement, the Company received an upfront cash payment of $150.2 million. The Company has identified the initial consideration for the Celgene Collaboration Agreement, which is the best estimated selling price, as the $150.2 million upfront payment under the Celgene Collaboration Agreement. The Company determined that each of the identified deliverables have the same period of performance (the ten year research collaboration term) and have the same pattern of revenue recognition, ratably over the period of performance. As a result, the $150.2 million in arrangement consideration was recorded in deferred revenue and will be recognized over the ten year research collaboration term. The Company recognized revenue of $5.1 million for the year ended December 31, 2015 in connection with the Celgene Collaboration Agreement. The Company also evaluated its own options pertaining to Celgene’s programs. If the Company exercises any of its options, it is required to make a payment equal to a percentage of the costs incurred by Celgene prior to the exercise of the option in connection with the research and development activities and regulatory activities for such development candidate. The percentage of costs to be paid varies based on the point in development of such product at the time the Company exercises its option. The Company will account for the payments as research and development expense upon the exercise of the related option. The Company determined that payments related to licenses that will be used in future research and development activities with no proven alternative future use at the time of acquisition by the Company should be expensed when incurred in accordance with the Company’s accounting policy. In addition, Celgene purchased 9,137,672 shares of the Company’s common stock at a price of $93.00 per share, resulting in gross proceeds of $849.8 million. The Company determined that this initial purchase of common stock combined with the embedded future stock purchase rights had a fair value of $849.8 million and this amount was recorded in equity. The Company evaluated and determined that the Top-Up Rights and Acquisition Rights granted to Celgene under the Purchase Agreement are not freestanding instruments as these rights are not legally detachable and separately exercisable from the Company’s common stock. In addition, the Company has further assessed whether the Top-Up Rights and Acquisition Rights should be accounted for as derivative instruments and determined that derivative accounting does not apply. The Company determined that the Top-Up Rights and Acquisition Rights are embedded and inseparable from the initial stock purchase and no subsequent remeasurement is necessary. Fred Hutchinson Cancer Research Center In October 2013, the Company entered into a collaboration agreement with FHCRC, focused on research and development of cancer immunotherapy products. The agreement has a six year term and can be extended if mutually agreed upon. The research is conducted under project orders containing plans and budgets approved by the parties. The Company recognized $10.3 million, $6.9 million, and $3.4 million of research and development expenses in connection with its collaboration agreement with FHCRC for the years ended December 31, 2015 and 2014, and for the period from August 5, 2013 to December 31, 2013, respectively. The Company granted FHCRC rights to certain share-based success payments. Under the terms of this arrangement, the Company may be required to make success payments to FHCRC based on increases in the estimated fair value of the Company’s common stock. The potential payments are based on multiples of increased value ranging from 5x to 40x based on a comparison of the fair value of the common stock relative to its original $4.00 issuance price. The payments are based on whether the value of the Company’s common stock meets or exceeds certain specified threshold values ascending from $20.00 per share to $160.00 per share, in each case subject to adjustment for any stock dividend, stock split, combination of shares, or other similar events. The aggregate success payments to FHCRC are not to exceed $375 million which would only occur at a stock valuation of $160.00 per share. In June 2014, the Company entered into an agreement with FHCRC in which it can offset certain indirect costs related to the collaboration projects conducted by FHCRC against any success payments. The term of the success payment agreement ranges from eight to eleven years depending upon when or if the company receives FDA approval of certain of its product candidates as specified in the agreement. The following table summarizes all possible FHCRC success payments, which are payable in cash or publicly-traded equity at the Company’s discretion: Multiple of Initial Equity Value at issuance 5.0x 7.5x 10.0x 15.0x 20.0x 25.0x 30.0x 35.0x 40.0x Per share common stock price required for payment $ 20.00 $ 30.00 $ 40.00 $ 60.00 $ 80.00 $ 100.00 $ 120.00 $ 140.00 $ 160.00 Success payment(s) (in millions) $ 10 $ 25 $ 40 $ 50 $ 50 $ 50 $ 50 $ 50 $ 50 The success payments will be owed if the value of the Company’s common stock on the contractually specified valuation measurement dates during the term of the success payment agreement equals or exceeds the above outlined multiples. The valuation measurement dates are triggered by events which include an initial public offering of the Company’s stock, a merger, an asset sale, or the sale of the majority of the shares held by certain of the Company’s stockholders or the last day of the term of the success payment agreement. If a higher success payment tier is first met at the same time a lower tier is first met, both tiers will be owed. Any previous success payments made to FHCRC are credited against the success payment owed as of any valuation measurement date, so that FHCRC does not receive multiple success payments in connection with the same threshold. A payment may be triggered on the first anniversary of the closing of the IPO (or the date that is 90 days following such anniversary, at the Company’s option, if the Company is contemplating a capital market transaction during such 90 day period). The value of any such success payment will be determined by the average trading price of a share of the Company’s common stock over the consecutive 90-day period preceding such determination date. In December 2015, success payments to FHCRC were triggered in the aggregate amount of $75.0 million, less indirect cost offsets of $3.3 million. These success payments represent the success payments identified on the table above for the 5.0x, 7.5x, and 10.0x Multiple of Initial Equity Value triggers. The Company elected to make the payment in shares of its common stock, and thereby issued 1,601,085 shares of its common stock to FHCRC in December 2015. In the future, the outstanding potential success payments to FHCRC are owed only if the criteria are met with the equity value at the 15.0x Multiple of Initial Equity Value or higher. The estimated fair value of the success payment obligation to FHCRC after giving effect to the success payments achieved in December 2015 was approximately $67.3 million and $139.1 million as of December 31, 2015 and 2014, respectively. With respect to the FHCRC success payment obligations, the Company recognized research and development expense of $44.3 million and $61.2 million in the years ended December 31, 2015 and 2014, respectively. The expense recorded in both periods represents the change in the FHCRC success payment liability during such periods, the success payment amounts achieved in 2015, and twelve months of accrued expense. The FHCRC success payment liabilities on the consolidated balance sheets as of December 31, 2015 and December 31, 2014 were $33.8 million and $61.2 million, respectively. The Company’s liability for share-based success payments under the FHCRC collaboration is carried at fair value and recognized as expense over the term of the six-year collaboration agreement. To determine the estimated fair value of the success payment liability the Company uses a Monte Carlo simulation methodology which models the future movement of stock prices based on several key variables. The following variables were incorporated in the calculation of the estimated fair value of the success payment liability as of the following balance sheet dates: December 31, Assumptions 2015 2014 Fair value of common stock $ 43.97 $ 52.22 Risk free interest rate 1.89% – 2.20 % 1.94% – 2.16 % Expected volatility 70 % 75 % Expected term (years) 5.79 – 8.79 6.79 – 9.79 The computation of expected volatility was estimated using a combination of available information about the historical volatility of stocks of similar publicly-traded companies for a period matching the expected term assumption and our historical and implied future volatility. The risk free interest rate and expected term assumptions depend on the estimated timing of FDA approval. In addition, the Company incorporated the estimated number and timing of valuation measurement dates in the calculation of the success payment liability. In October 2013, the Company entered into a license agreement with FHCRC, pursuant to which the Company acquired an exclusive, worldwide, sublicensable license under certain patent rights, and a non-exclusive, worldwide, sublicensable license under certain technology, to research, develop, manufacture, improve, and commercialize products and processes covered by such patent rights or incorporating such technology for all therapeutic uses for the treatment of human cancer. The patents and patent applications covered by this agreement are directed, in part, to CAR constructs, including target specific constructs and customized spacer regions, TCR constructs, and their use for immunotherapy. The Company classifies on the consolidated statement of operations payments accrued or made under its licensing arrangements based on the underlying nature of the expense. Expenses related to the reimbursement of legal and patent costs are classified as general and administrative because the nature of the expense is not related to the research or development of the technologies the Company is licensing. The Company also agreed to pay FHCRC annual maintenance fees, milestone payments, and royalties as a percentage of net sales of licensed products. After five years the Company is obligated to pay a $0.1 million minimum annual royalty, with such payments creditable against royalties. Milestone payments to FHCRC of up to an aggregate of $6.8 million per licensed product, including JCAR014 and JCAR017, are triggered upon the achievement of specified clinical and regulatory milestones and are not creditable against royalties. The Company may terminate the license agreement at any time with advance written notice. Memorial Sloan Kettering Cancer Center In November 2013, the Company entered into a sponsored research agreement with MSK, focused on research and development relating to chimeric antigen receptor T cell technology. The research is conducted under project orders containing plans and budgets approved by the parties. The Company also entered into a master clinical study agreement with MSK for clinical studies to be conducted at MSK on the Company’s behalf. Each such study will be conducted in accordance with a written plan and budget and protocol, or separate clinical trial agreement, approved by the parties. The Company recognized $4.7 million, $2.5 million, and $0.5 million of research and development expenses in connection with its research and clinical agreements with MSK for the years ended December 31, 2015 and 2014, and for the period from August 5, 2013 to December 31, 2013, respectively. The Company granted MSK rights to certain share-based success payments. Under the terms of this arrangement, the Company may be required to make success payments to MSK based on the increases in the estimated fair value of the Company’s common stock. The potential payments are based on multiples of increased value ranging from 10x to 30x based on a comparison of the fair value of the common stock relative to its original $4.00 issuance price. The payments are based on whether the value of the Company’s common stock meets or exceeds certain specified threshold values ascending from $40.00 per share to $120.00 per share, in each case subject to adjustment for any stock dividend, stock split, combination of shares, or other similar events. The aggregate success payments to MSK are not to exceed $150 million, which would only occur at a stock valuation of $120.00 per share. In October 2015, the Company entered into an agreement with MSK in which certain indirect costs related to certain clinical studies and research projects conducted by MSK are creditable against any success payments, and the Company amended this agreement in December 2015. The term of the success payment agreement ranges from eight to eleven years depending upon when or if the company receives FDA approval of certain of its product candidates as specified in the agreement. The following table summarizes all possible MSK success payments, which are payable in cash or publicly-traded equity at the Company’s discretion: Multiple of Initial Equity Value at issuance 10.0x 15.0x 30.0x Per share common stock price required for payment $ 40.00 $ 60.00 $ 120.00 Success payment(s) (in millions) $ 10 $ 70 $ 70 The success payments will be owed, if the value of the Company’s common stock on contractually specified valuation measurement dates equals or exceeds the above outlined multiples. The valuation measurement dates are triggered by events which include an initial public offering of the Company’s stock, a merger, an asset sale, or the sale of the majority of the shares held by certain of the Company’s stockholders or the last day of the term of the success payment agreement. If a higher success payment tier is met at the same time a lower tier is met, both tiers will be owed. Any previous success payments made to MSK are credited against the success payment owed as of any valuation measurement date, so that MSK does not receive multiple success payments in connection with the same threshold. A payment may be triggered on the first anniversary of the closing of the IPO (or the date that is 90 days following such anniversary, at the Company’s option, if the Company is contemplating a capital market transaction during such 90 day period). The value of any such success payment will be determined by the average trading price of a share of the Company’s common stock over the consecutive 90-day period preceding such determination date. In December 2015, a success payment to MSK was triggered in the amount of $10.0 million, less indirect cost offsets that will be determined at the time of payment in March 2016. This success payment represents the success payment identified on the table above for the 10.0x Multiple of Initial Equity Value trigger. Going forward, the only potential remaining success payment obligations relate to the 15.0x and 30.0x Multiple of Initial Equity Value. As of December 31, 2015 and 2014, the estimated fair value of the success payment obligation to MSK after giving effect to the success payment achieved in December 2015, was approximately $48.9 million and $56.8 million, respectively. With respect to the MSK success payment obligations, the Company recognized research and development expense of $7.3 million and $23.7 million in the years ended December 31, 2015 and 2014, respectively. The expense recorded in both periods represents the change in the MSK success payment liability during such periods, the success payment amount achieved in 2015, and twelve months of accrued expense. The MSK success payment liabilities on the consolidated balance sheets as of December 31, 2015 and December 31, 2014 were $31.0 million and $23.7 million, respectively. The Company’s liability for share-based success payments under the MSK collaboration is carried at fair value and recognized as expense over the term of the five-year collaboration agreement. To determine the estimated fair value of the success payment liability the Company uses a Monte Carlo simulation methodology which models the future movement of stock prices based on several key variables. The following variables were incorporated in the calculation of the estimated fair value of the success payment liability as of the following balance sheet dates: December 31, Assumptions 2015 2014 Fair value of common stock $ 43.97 $ 52.22 Risk free interest rate 1.91% – 2.20 % 1.95% – 2.16 % Expected volatility 70 % 75 % Expected term (years) 5.89 – 8.89 6.89 – 9.89 The computation of expected volatility was estimated using a combination of available information about the historical volatility of stocks of similar publicly-traded companies for a period matching the expected term assumption and our historical volatility. The risk free interest rate and expected term assumptions depend on the estimated timing of FDA approval. In addition, the Company incorporated the estimated number and timing of valuation measurement dates in the calculation of the success payment liability. In November 2013, the Company entered into a license agreement with MSK, pursuant to which the Company acquired a worldwide, sublicensable license to specified patent rights and intellectual property rights related to certain know-how to develop, make, and commercialize licensed products and to perform services for all therapeutic and diagnostic uses, which license is exclusive with respect to such patent rights and tangible materials within such know-how, and non-exclusive with respect to such know-how and related intellectual property rights. The patents and patent applications covered by this agreement are directed, in part, to CAR constructs, including bispecific and armored CARs, and their use for immunotherapy. The Company recorded $6.9 million in the period from August 5, 2013 to December 31, 2013 for the upfront license fee, which was recorded as research and development expense. The Company also agreed to pay MSK milestone payments and royalties as a percentage of net sales of licensed products and services by us or our affiliates and sublicensees. After five years the Company is obligated to pay a $0.1 million minimum annual royalty, with such payments credible against royalties. Milestone payments to MSK of up to an aggregate of $6.8 million per licensed product, including JCAR015, are triggered upon the achievement of specified clinical and regulatory milestones and are not creditable against royalties. The Company may terminate the license agreement at any time with advance written notice, but if the Company has commenced the commercialization of licensed products, the Company can only terminate at will if it ceases all development and commercialization of licensed products. St. Jude Children’s Research Hospital/Novartis In December 2013, the Company entered into an agreement with St. Jude (“St. Jude License Agreement”), pursuant to which the Company (1) obtained control over, and the obligation to pursue and defend, St. Jude’s causes of action in Trustees of the University of Pennsylvania v. St. Jude Children’s Research Hospital, Civil Action No. 2:13-cv-01502-SD (E.D. Penn.), which concerned both U.S. Patent No. 8,399,645 (the “’645 Patent”) and a contractual dispute between St. Jude and the Trustees of the University of Pennsylvania (“Penn”) and (2) acquired an exclusive, worldwide, royalty-bearing license under certain patent rights owned by St. Jude, including the ’645 Patent, to develop, make, and commercialize licensed products and services for all therapeutic, diagnostic, preventative, and palliative uses. The patents and patent applications covered by this agreement are directed, in part, to CAR constructs capable of signaling both a primary and a costimulatory pathway. Together with St. Jude, the Company was a party in, and was adverse to Penn and Novartis Pharmaceutical Corporation (“Novartis”) in, that litigation (the “Penn litigation”),

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	12 Months Ended
	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash Equivalents and Marketable Securities	5. Cash Equivalents and Marketable Securities The following tables summarize the estimated fair value of our cash equivalents and marketable securities and the gross unrealized holding gains and losses (in thousands): December 31, 2015 Amortized Gross Gross Estimated Fair Cash equivalents: Money market funds $ 177,164 $ — $ — $ 177,164 Commercial paper 45,352 — — 45,352 U.S. government and agency securities 2,000 — — 2,000 Corporate debt securities 5,040 — — 5,040 Total cash equivalents 229,556 — — 229,556 Marketable securities: Commercial paper 73,078 — — 73,078 U.S. government and agency securities 470,519 2 (485 ) 470,036 Corporate debt securities 148,143 1 (245 ) 147,899 Total marketable securities 691,740 3 (730 ) 691,013 Long-term marketable securities: U.S. government and agency securities 204,551 1 (770 ) 203,782 Corporate debt securities 65,898 33 (195 ) 65,736 Equity securities 7,190 — (3,820 ) 3,370 Total long-term marketable securities $ 277,639 $ 34 $ (4,785 ) $ 272,888 December 31, 2014 Amortized Gross Unrealized Gross Unrealized Estimated Fair Cash equivalents: Money market funds $ 223,745 $ — $ — $ 223,745 Commercial paper 13,294 — — 13,294 U.S. government and agency securities 7,582 — — 7,582 Corporate debt securities 1,702 — — 1,702 Total cash equivalents 246,323 — — 246,323 Marketable securities: Commercial paper 1,999 — — 1,999 U.S. government and agency securities 47,868 — (21 ) 47,847 Corporate debt securities 29,863 — (37 ) 29,826 Total marketable securities 79,730 — (58 ) 79,672 Long-term marketable securities: U.S. government and agency securities 34,898 — (25 ) 34,873 Corporate debt securities 3,544 1 (7 ) 3,538 Total long-term marketable securities $ 38,442 $ 1 $ (32 ) $ 38,411 The following tables summarize the gross unrealized holding losses and fair value for investments in an unrealized loss position, and the length of time that individual securities have been in a continuous loss position (in thousands): December 31, 2015 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Marketable securities: U.S. government and agency securities $ 457,641 $ (485 ) $ — $ — $ 457,641 $ (485 ) Corporate debt securities 144,499 (245 ) — — 144,499 (245 ) Total marketable securities 602,140 (730 ) — — 602,140 (730 ) Long-term marketable securities: U.S. government and agency securities 190,767 (770 ) — — 190,767 (770 ) Corporate debt securities 50,591 (195 ) — — 50,591 (195 ) Equity securities 3,370 (3,820 ) — — 3,370 (3,820 ) Total long-term marketable securities $ 244,728 $ (4,785 ) $ — $ — $ 244,728 $ (4,785 ) December 31, 2014 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Marketable securities: U.S. government and agency securities $ 43,332 $ (21 ) $ — $ — $ 43,332 $ (21 ) Corporate debt securities 26,611 (37 ) — — 26,611 (37 ) Total marketable securities 69,943 (58 ) — — 69,943 (58 ) Long-term marketable securities: U.S. government and agency securities 33,873 (25 ) — — 33,873 (25 ) Corporate debt securities 2,003 (7 ) — — 2,003 (7 ) Total long-term marketable securities $ 35,876 $ (32 ) $ — $ — $ 35,876 $ (32 ) The Company evaluated its securities for other-than-temporary impairment and considers the decline in market value for the securities to be primarily attributable to current economic and market conditions. For the debt securities, it is not more likely than not that the Company will be required to sell the securities, and the Company does not intend to do so prior to the recovery of the amortized cost basis. The unrealized loss for equity securities is related to the Company’s investment in Fate Therapeutics. The Company has evaluated the near-term prospects of the Fate Therapeutics investment in relation to the severity and duration of the impairment and based on that evaluation, the Company has the ability and intent to hold this investment until a recovery of fair value. Based on this analysis, these marketable securities were not considered to be other-than-temporarily impaired as of December 31, 2015 and 2014. All of our marketable securities have an effective maturity date of three years or less and are available for use and therefore classified as available-for-sale.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	6. Fair Value Measurements The following tables set forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands): December 31, 2015 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 177,164 $ — $ — $ 177,164 Commercial paper — 118,430 — 118,430 U.S. government and agency securities — 675,818 — 675,818 Corporate debt securities — 218,675 — 218,675 Equity securities 3,370 — — 3,370 Total financial assets $ 180,534 $ 1,012,923 $ — $ 1,193,457 Financial Liabilities: Success payment liabilities $ — $ — $ 64,829 $ 64,829 Contingent consideration — — 37,266 37,266 Total financial liabilities $ — $ — $ 102,095 $ 102,095 December 31, 2014 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 223,745 $ — $ — $ 223,745 Commercial paper — 15,293 — 15,293 U.S. government and agency securities — 90,302 — 90,302 Corporate debt securities — 35,066 — 35,066 Total financial assets $ 223,745 $ 140,661 $ — $ 364,406 Financial Liabilities: Success payment liabilities $ — $ — $ 84,920 $ 84,920 Total financial liabilities $ — $ — $ 84,920 $ 84,920 The Company measures the fair value of money market funds based on quoted prices in active markets for identical assets or liabilities. The Level 2 marketable securities include U.S. government and agency securities, corporate debt securities, and commercial paper and are valued either based on recent trades of securities in inactive markets or based on quoted market prices of similar instruments and other significant inputs derived from or corroborated by observable market data. The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands): Success Contingent Total Balance at December 31, 2013 $ — $ — $ — Additions — — — Changes in fair value (1) 84,920 — 84,920 Balance at December 31, 2014 84,920 — 84,920 Additions — 37,188 37,188 Payments (71,648 ) — (71,648 ) Changes in fair value (1) 51,557 78 51,635 Balance at December 31, 2015 $ 64,829 $ 37,266 $ 102,095 (1) The amount of success payments achieved and changes in fair value for success payment liabilities and contingent consideration are recorded in research and development expense in the consolidated statements of operations. As of December 31, 2015 and 2014, the estimated fair value of the success payment obligations after giving effect to the success payments achieved by FHCRC and MSK was approximately $116.2 million and $195.9 million, respectively. Included in research and development expense for the years ended December 31, 2015 and 2014 were success payment expenses of $51.6 million and $84.9 million, respectively. There was no expense in 2013 related to the success payments. See Note 4, Collaboration and License Agreements, for additional discussion of estimated fair value of the success payment obligations. The Company utilizes significant estimates and assumptions in determining the estimated success payment and contingent consideration liabilities and associated expense at each balance sheet date. A small change in the Company’s stock price may have a relatively large change in the estimated fair value of the success payment liability and associated expense. In connection with the acquisitions of Stage and X-Body, the Company also agreed to pay additional amounts based on the achievement of certain milestones. This contingent consideration is measured at fair value and is based on significant inputs not observable in the market, which represents a Level 3 measurement within the fair value hierarchy. The valuation of contingent consideration uses assumptions the Company believes would be made by a market participant. The Company assesses these estimates on an on-going basis as additional data impacting the assumptions is obtained. Contingent consideration may change significantly as development progresses and additional data are obtained, impacting the Company’s assumptions regarding probabilities of successful achievement of related milestones used to estimate the fair value of the liability and the timing in which they are expected to be achieved. In evaluating the fair value information, judgment is required to interpret the market data used to develop the estimates. The estimates of fair value may not be indicative of the amounts that could be realized in a current market exchange. Accordingly, the use of different market assumptions and/or different valuation techniques could result in materially different fair value estimates. The significant unobservable inputs used in the measurement of fair value of the Company’s contingent consideration are probabilities of successful achievement of the milestones, the period in which these milestones are expected to be achieved ranging from 2016 to 2043, and a discount rate of 17.0%. Significant increases or decreases in any of the probabilities of success would result in a significantly higher or lower fair value measurement, respectively. Significant increases or decreases in these other inputs would result in a significantly lower or higher fair value measurement, respectively. As of December 31, 2015, the estimated fair value of the contingent consideration associated with the Stage acquisition was $28.3 million. As of December 31, 2015, the estimated fair value of the contingent consideration associated with the X-Body acquisition was $9.0 million. The Company recognized an expense of $0.1 million in research and development expense in the year ended December 31, 2015 related to the change in fair value of the contingent consideration.

Property and Equipment, Net

Property and Equipment, Net	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Property and Equipment, Net	7. Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): December 31, 2015 2014 Construction in progress $ 23,214 $ — Build-to-suit asset 9,910 — Laboratory equipment 9,706 3,921 Computer equipment, software and other 773 198 Leasehold improvements 300 98 Property and equipment, at cost 43,903 4,217 Less: Accumulated depreciation (1,817 ) (199 ) Property and equipment, net $ 42,086 $ 4,018 Depreciation expense related to property and equipment was $1.6 million and $0.2 million for the years ended December 31, 2015 and 2014, respectively. Depreciation expense was immaterial in 2013.

Accrued Liabilities and Other C

Accrued Liabilities and Other Current Liabilities	12 Months Ended
	Dec. 31, 2015
Payables and Accruals [Abstract]
Accrued Liabilities and Other Current Liabilities	8. Accrued Liabilities and Other Current Liabilities Accrued liabilities and other current liabilities consisted of the following (in thousands): December 31, 2015 2014 Accrued clinical expenses $ 7,174 $ 564 Accrued research and development expenses 7,132 2,724 Accrued bonus expense 7,054 3,106 Accrued employee expenses 3,281 531 Accrued milestones 2,827 — Accrued legal expenses 1,987 4,309 Accrued offering costs — 1,456 Other 3,921 1,887 Total accrued liabilities and other current liabilities $ 33,376 $ 14,577

Build-to-Suit Lease Obligation

Build-to-Suit Lease Obligation	12 Months Ended
	Dec. 31, 2015
Leases [Abstract]
Build-to-Suit Lease Obligation	9. Build-to-Suit Lease Obligation In February 2015, the Company entered into a lease for an approximately 68,000 square foot manufacturing facility in Bothell, Washington, which commenced in March 2015. The Company is responsible for the leasehold improvements required to remodel the facility and bears the majority of the construction risk. ASC 840-40, Leases—Sale-Leaseback Transactions, requires the Company to be considered the owner of the building solely for accounting purposes during the construction period, even though it is not the legal owner. In connection with the accounting for this transaction, the Company capitalized $9.9 million as a build-to-suit property within property and equipment, net and recognized a corresponding build-to-suit lease obligation for the same amount. The Company bifurcates its lease payments into a portion allocated to the building and a portion allocated to the parcel of land on which the building has been built. The portion of the lease payments allocated to the land is treated for accounting purposes as operating lease payments, and therefore is recorded as rent expense in the consolidated statements of operations. The portion of the lease payments allocated to the building is further bifurcated into a portion allocated to interest expense and a portion allocated to reduce the build-to-suit lease obligation. At December 31, 2015, $0.4 million of the build-to-suit lease obligation, representing the expected reduction in the liability over the next twelve months, is classified as a current liability and $9.3 million is classified as a non-current liability on the consolidated balance sheets.

Common Stock

Common Stock	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Common Stock	10. Common Stock As of December 31, 2015 and 2014, there were 97,247,058 shares and 82,073,647 shares of common stock outstanding, excluding 5,153,445 shares and 8,352,714 shares, respectively, of restricted stock outstanding that are subject to vesting requirements. As of December 31, 2015 and 2014, the Company had reserved 5,614,926 shares and 2,720,351 shares of common stock for future issuance upon the exercise of outstanding stock options and vesting of outstanding RSUs. Each share of common stock is entitled to one vote, subject to any special voting rights of preferred stock, none of which was outstanding as of December 31, 2015 and 2014.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation	11. Stock-Based Compensation Equity Incentive Plans Until the IPO, the Company maintained and granted restricted stock awards and option awards under the 2013 Stock Incentive Plan (the “2013 Plan”) for employees, directors, consultants, and advisors to the Company. The 2013 Plan terminated as of the IPO as to future awards, but will continue to govern restricted stock awards and option awards previously granted thereunder. Upon termination of the 2013 Plan, the 453,547 shares that were then unissued and available for future award under the 2013 Plan became available under the 2014 Equity Incentive Plan (the “2014 Plan”), described below. In December 2014, the Company’s board of directors adopted the 2014 Plan. The 2014 Plan became effective the day prior to the effective date of the registration statement for the Company’s IPO, and enables the grant of incentive and non-qualified stock options, restricted stock awards, restricted stock unit awards, stock appreciation rights, and other stock-based awards to employees, directors, consultants, and advisors to the Company. Terms of the awards, including vesting requirements, are determined by the Company’s board of directors or by a committee appointed by our board of directors. The 2014 Plan provides for an initial reserve of 6,200,000 shares, plus the 453,547 shares initially transferred from the 2013 Plan, and any share awards that subsequently are forfeited or lapse unexercised under the 2013 Plan. The 2014 Plan provides for an annual increase in the shares available for issuance thereunder, to be added on the first day of each fiscal year, beginning with the year ending December 31, 2015 and continuing until the expiration of the 2014 Plan, equal to the lesser of (i) four percent (4%) of the outstanding shares of the Company’s common stock on the last day of the immediately preceding fiscal year or (ii) such number of shares determined by the board of director or an authorized committee of the board of directors; provided, however, that such determination under clause (ii) will be made no later than the last day of the immediately preceding fiscal year. As of December 31, 2015, the total number of shares available for issuance pursuant to future awards under the 2014 Plan was 7,021,850. As a result of the operation of this provision, on January 1, 2016, an additional 4,096,020 shares became available for issuance under the 2014 Plan. Generally, awards granted by the Company under the 2013 Plan and 2014 Plan vest over four years. 2014 Employee Stock Purchase Plan In December 2014, the Company’s board of directors adopted the 2014 employee stock purchase plan (the “ESPP”). The ESPP is administered by the Company’s board of directors or by a committee appointed by the board of directors. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. The initial offering period under the ESPP began on December 19, 2014 and ended on November 16, 2015, on which date participating employees purchased shares at $20.40 per share, which is 85% of the price to the public of a share of the Company’s common stock in its IPO. Following the initial offering period, the ESPP provides for consecutive six-month offering periods beginning on the first trading day on or after November 15 and May 15 of each year, and at the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last day of the offering period. The Company initially reserved 1,500,000 shares of common stock for issuance under the ESPP. As of December, 31, 2015, 67,664 shares had been issued under the ESPP. As of December 31, 2014, no shares had been issued under the ESPP. The ESPP also provides for an annual share increase, to be added on the first day of each fiscal year, beginning with the year ending December 31, 2015 and continuing until the expiration of the ESPP, equal to the lesser of (i) one and a half percent (1.5%) of the outstanding shares of the Company’s common stock on the last day of the immediately preceding fiscal year or (ii) such number of shares determined by the board of directors or authorized committee of the board of directors. As of December 31, 2015, the total number of shares available for future issuance pursuant to the ESPP was 2,788,731. As a result of the operation of this provision, on January 1, 2016, an additional 1,536,008 shares became available for issuance under the ESPP. Stock-Based Compensation Stock-based compensation expense is recognized in our consolidated statements of operations as follows (in thousands): Year Ended December 31, Period from December 31, 2013 2015 2014 Research and development $ 17,089 $ 2,908 $ 125 General and administrative 14,852 3,596 — Total stock-based compensation expense (1) $ 31,941 $ 6,504 $ 125 (1) Included in stock-based compensation expense recognized for the years ended December 31, 2015 and 2014, is $8.1 million and $2.8 million, respectively, related to service providers other than our employees, scientific founders, and directors, including $6.2 million and $2.5 million, respectively, for a former co-founding director who became a consultant upon his departure from the board of directors. As of December 31, 2015, there was $107.2 million of total unrecognized stock-based compensation cost related to employees. Of the $107.2 million in unrecognized stock-based compensation costs, $20.3 million is related to restricted stock and RSUs, and $86.9 million is related to stock options. As of December 31, 2015, the Company expects to recognize these costs over a remaining weighted average period of 2.39 years for restricted stock and RSUs, and 3.06 years for stock options. Restricted Stock and RSUs A summary of the Company’s restricted stock and RSU activity is as follows: Shares Weighted Average Fair Unvested shares as of December 31, 2014 8,352,714 $ 1.46 Granted 395,987 49.51 Vested (3,245,512 ) 0.51 Forfeited (26,589 ) 0.60 Unvested shares as of December 31, 2015 5,476,600 $ 3.72 Management estimates expected forfeitures and recognizes compensation costs only for those equity awards expected to vest. The fair value of awards vested during the years ended December 31, 2015 and 2014 and for the period from August 5, 2013 to December 31, 2013 was $158.5 million, $21.4 million, and $0.4 million, respectively. Stock Options A summary of the Company’s stock option activity is as follows: Number of Weighted Weighted Aggregate Outstanding as of December 31, 2014 2,720,351 $ 7.23 Granted 2,914,406 49.08 Exercised (268,765 ) 7.39 Cancelled (147,053 ) 19.20 Outstanding as of December 31, 2015 5,218,939 $ 30.25 9.13 $ 86,609 Exercisable as of December 31, 2015 806,477 $ 16.17 8.70 $ 23,160 The fair value of each stock option granted has been determined using the Black-Scholes option pricing model. The material factors incorporated in the Black-Scholes model in estimating the fair value of the options granted to employees, directors, and consultants included the following: December 31, Assumptions 2015 2014 Risk free interest rate 1.53% – 2.35 % 1.59% – 2.17 % Expected volatility 70% – 80 % 75 % Expected life (years) 6.02 – 10 6.25 – 10 Expected dividend yield 0 % 0 % For employees, scientific founders, and directors, the expected life was calculated based on the simplified method as permitted by the SEC Staff Accounting Bulletin No. 110, Share-Based Payment

Accumulated Other Comprehensive

Accumulated Other Comprehensive Income (Loss)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Accumulated Other Comprehensive Income (Loss)	12. Accumulated Other Comprehensive Income (Loss) The components of accumulated other comprehensive income (loss) and the adjustments to other comprehensive income (loss) are as follows (in thousands): Foreign Currency Net Unrealized Available-For-Sale Accumulated Other Balance at December 31, 2013 $ — $ — $ — Other comprehensive loss — (90 ) (90 ) Balance at December 31, 2014 — (90 ) (90 ) Other comprehensive loss (605 ) (5,388 ) (5,993 ) Balance at December 31, 2015 $ (605 ) $ (5,478 ) $ (6,083 )

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	13. Income Taxes The Company recorded an income tax benefit of $2.8 million on a pre-tax loss of $242.1 million for year ended December 31, 2015. Of the $2.8 million total tax benefit, $1.7 million relates to our Germany subsidiary’s net loss incurred in the period from the acquisition date to December 31, 2015. The remaining $1.1 million of income tax benefit relates to the release of valuation allowance on the U.S. deferred tax assets as a result of the deferred tax liabilities established for definite lived intangible assets from the acquisition of X-Body. The Celgene Collaboration Agreement became effective on July 31, 2015. In addition, on August 4, 2015 the Initial Closing under the Purchase Agreement with Celgene occurred. The Company does not expect that the $849.8 million in consideration allocable to the sale of the Company’s shares and future rights to purchase shares of common stock of the Company under the Purchase Agreement will result in gain or loss in accordance with the Internal Revenue Code. The Company has determined that the $150.2 million consideration allocable to the upfront payment for the Celgene Collaboration Agreement is fully taxable, partially in 2015, with the remainder in 2016. Loss before income taxes is attributable to the following tax jurisdictions (in thousands): Year Ended December 31, Period from August 5, 2013 to December 31, 2013 2015 2014 United States $ 236,028 $ 243,407 $ 51,820 Foreign 6,108 — — Loss before income taxes $ 242,136 $ 243,407 $ 51,820 The components of the benefit for income taxes are as follows (in thousands): Year Ended December 31, Period from August 5, 2013 to December 31, 2013 2015 2014 Deferred: United States $ 1,100 $ — $ — Foreign 1,660 — — Total deferred 2,760 — — Provision for income taxes $ 2,760 $ — $ — As of December 31, 2015 and 2014, the Company had U.S. federal net operating loss (“NOL”) carryforwards of approximately $167.3 million and $51.1 million, respectively, which are available to reduce future taxable income. Of these NOL carryforwards, a $3.5 million benefit will be recorded to equity when utilized. The Company also had U.S. federal and state tax credits of $14.6 million and $1.8 million as of December 31, 2015 and 2014, respectively, which may be used to offset future tax liabilities. The NOL and tax credit carryforwards will begin to expire in 2033. The NOL and tax credit carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant stockholders over a three year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code of 1986 (“IRC”). This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities. Subsequent ownership changes may further affect the limitation in future years. The Company also has German NOL carryforwards of $4.9 million, which have an indefinite carryforward period. A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations follows: Year Ended December 31, Period from August 5, 2013 to December 31, 2013 2015 2014 Federal statutory tax 35.0 % 34.0 % 34.0 % Foreign tax rate differential (0.1 ) — — Valuation allowance (36.2 ) (32.4 ) (30.0 ) Tax credits 3.8 0.7 0.2 Other (1.4 ) (2.3 ) (4.2 ) Total 1.1 % 0.0 % 0.0 % The effective tax rate for the years ended December 31, 2015 and 2014, and the period from August 5, 2013 to December 31, 2013, is different from the federal statutory tax rate primarily due to a valuation allowance against deferred tax assets as a result of insufficient sources of income. The principal components of the Company’s net deferred tax liabilities are as follows (in thousands): December 31, 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 56,862 $ 17,391 Tax credit carryforwards 14,561 1,799 Acquired technology 57,369 45,534 Success payments 47,745 28,872 Stock compensation 4,342 115 Other 5,019 1,430 Gross deferred tax assets 185,898 95,141 Valuation allowance (183,597 ) (94,368 ) Deferred tax assets, net of valuation allowance 2,301 773 Deferred tax liabilities: Acquired technology (10,540 ) — Other (707 ) (773 ) Deferred tax liabilities (11,247 ) (773 ) Net deferred tax liabilities $ (8,946 ) $ — The valuation allowance relates primarily to net U.S. deferred tax assets from operating losses, research and development tax credit carryforwards, amounts paid and accrued to enter into various agreements for which the tax treatment requires capitalization and amortization, and success-based payments that are accrued but not yet paid for tax purposes. The Company’s deferred tax liability relates primarily to technology acquired in the acquisition of Stage. The Company will continue to maintain a full valuation allowance on its net U.S. deferred tax assets. The assessment regarding whether a valuation allowance is required considers both positive and negative evidence when determining whether it is more-likely-than-not that deferred tax assets are recoverable. In making this assessment, significant weight is given to evidence that can be objectively verified. In its evaluation, the Company considered its cumulative loss in recent years and its forecasted losses in the near-term as significant negative evidence. Based upon a review of the four sources of income identified within ASC 740, the Company determined that the negative evidence outweighed the positive evidence and a full valuation allowance on its U.S. net deferred tax assets will be maintained. The Company will continue to assess the realizability of its deferred tax assets going forward and will adjust the valuation allowance as needed. Increases in the valuation allowance were $89.2 million and $78.8 million for the years ended December 31, 2015 and 2014, respectively. The Company has determined that it is more-likely-than-not that it will realize the benefit of the losses for its Germany subsidiary and has not recorded a valuation allowance against the German deferred tax assets. The Company follows the provisions of ASC 740, Accounting for Income Taxes

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	14. Commitments and Contingencies Leases The Company has entered into various non-cancelable lease agreements for its office, laboratory, and manufacturing spaces with original lease periods expiring between 2016 and 2026. In addition to minimum rent, certain leases require payment of real estate taxes, insurance, common area maintenance charges and other executory costs. These executory costs are not included in the table below. Certain of these arrangements have free or escalating rent payment provisions. The Company recognizes rent expense under such arrangements on a straight-line basis over the effective term of each lease. The following table summarizes the Company’s future minimum lease commitments as of December 31, 2015 (in thousands): Year ending December 31: 2016 $ 3,890 2017 4,983 2018 10,652 2019 10,901 2020 11,156 Thereafter 42,031 Total minimum lease payments $ 83,613 Rent expense for the years ended December 31, 2015 and 2014, and for the period from August 5, 2013 to December 31, 2013 was $2.3 million, $0.9 million, and $0.1 million, respectively. Litigation From time to time, the Company may become involved in litigation or proceedings relating to claims arising from the ordinary course of business. In connection with the entry by the Company into its exclusive license agreement with St. Jude in December 2013, the Company acquired control of St. Jude’s causes of action in the Penn litigation, which concerns both a patent exclusively licensed to the Company by St. Jude and a contractual dispute between St. Jude and Penn. Together with St. Jude, the Company was a party in, and was adverse to Penn and Novartis Pharmaceutical Corporation in, that litigation, which was settled by the parties in April 2015. Under a separate agreement with St. Jude, the Company agreed to reimburse a percentage of St. Jude’s reasonable legal fees incurred in connection with the litigation. For the years ended December 31, 2015 and 2014, and for the period from August 5, 2013 to December 31, 2013, the Company recorded litigation expense of $5.5 million, $3.6 million, and $0.2 million, respectively, in the statements of operations for such legal reimbursements.

Related-Party Transactions

Related-Party Transactions	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related-Party Transactions	15. Related-Party Transactions The Company is party to the Celgene Collaboration Agreement, the Purchase Agreement, a voting agreement, and a registration rights agreement with Celgene, who is a holder of more than 5% of the Company’s common stock. See Note 4, Collaboration and License Agreements.

Employee Benefit Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2015
Postemployment Benefits [Abstract]
Employee Benefit Plan	16. Employee Benefit Plan In January 2014, the Company adopted a 401(k) retirement and savings plan (the “401(k) Plan”) covering all employees. The 401(k) Plan allows employees to make pre- and post-tax contributions up to the maximum allowable amount set by the IRS. The Company does not make matching contributions to the 401(k) Plan on behalf of participants.

Selected Quarterly Financial Da

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data	17. Selected Quarterly Financial Data (Unaudited) The following table contains quarterly financial information for the years ended December 31, 2015 and 2014. The unaudited quarterly information has been prepared on a basis consistent with the audited consolidated financial statements and includes all adjustments that the Company considers necessary for a fair presentation of the information shown. The operating results for any fiscal quarter are not necessarily indicative of the operating results for a full fiscal year or for any future period and there can be no assurances that any trend reflected in such results will continue in the future. Year Ended December 31, 2015 First Second Third Fourth (In thousands, except per share data) Loss from operations (1) (65,160 ) (67,965 ) (23,533 ) (87,442 ) Net loss (64,965 ) (65,958 ) (23,240 ) (85,213 ) Net loss per share attributable to common stockholders, basic and diluted (0.79 ) (0.79 ) (0.26 ) (0.89 ) Year Ended December 31, 2014 First Second Third Fourth (In thousands, except per share data) Loss from operations (8,320 ) (12,680 ) (19,818 ) (191,940 ) Net loss (8,949 ) (22,769 ) (19,818 ) (191,871 ) Deemed dividends upon issuance of convertible preferred stock — (15,357 ) (52,107 ) — Net loss attributable to common stockholders (8,949 ) (38,126 ) (71,925 ) (191,871 ) Net loss per share attributable to common stockholders, basic and diluted (1.41 ) (5.80 ) (10.50 ) (13.68 ) (1) Included in loss from operations is non-cash expense associated with the success payment liabilities to FHCRC and MSK attributable to the change in value and elapsed service period as follows: Year Ended December 31, 2015 First Second Third Fourth (In thousands) Non-cash succes payment expense (gain) included in loss from operations 38,911 3,961 (25,586 ) 34,273 (2) Included in loss from operations in the second quarter of 2015 is $30.8 million in upfront fees associated with the Editas and Fate collaborations. (3) Included in loss from operations in the fourth quarter of 2014 is $83.4 million associated with the portion of the success payment liability to FHCRC and MSK attributable to the elapsed service period and $84.1 million in upfront fees to acquire technology related to JCAR018, $20.0 million of which was paid in cash and $64.1 million was paid through the issuance of common stock.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	18. Subsequent Events In January 2016, the Company acquired AbVitro Inc., a company with a leading next-generation single cell sequencing platform. As consideration for the AbVitro Inc. acquisition, the Company paid approximately $78 million in cash and issued 1,289,188 shares of its common stock. There are no contingent consideration obligations under the terms of the AbVitro Inc. acquisition. The Company has not yet completed the initial accounting for this business combination. In January 2016, the first clinical milestone of $20.0 million was achieved under the Company’s license agreement with Opus Bio, and the Company issued 408,068 shares of its common stock as payment.

Significant Accounting Polici27

Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation and Use of Estimates	Basis of Presentation and Use of Estimates The accompanying consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”). The consolidated financial statements include the accounts of Juno Therapeutics, Inc. and its wholly-owned subsidiaries. All significant intercompany transactions and balances are eliminated in consolidation. The preparation of the Company’s consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from such estimates. The Company utilizes significant estimates and assumptions in determining the estimated success payment and contingent consideration liabilities and associated expense at each balance sheet date. A small change in the Company’s stock price may have a relatively large change in the estimated fair value of the success payment liability and associated expense. Changes in the probabilities and estimated timing of milestones used in the calculation of the contingent consideration liability may have a relatively large impact of the resulting liability and associated expense. Prior to becoming a public company, the Company utilized significant estimates and assumptions in determining the fair value of its common stock for financial reporting purposes. The Company recorded expense for restricted stock grants at prices not less than the fair market value of its common stock as determined by the board of directors, taking into consideration input from management and independent third-party valuation analysis, and in accordance with the AICPA Accounting and Valuation Guide, Valuation of Privately-Held Company Equity Securities Issued as Compensation. The estimated fair value of the Company’s common stock was based on a number of objective and subjective factors, including external market conditions affecting the biotechnology industry sector and the prices at which the Company sold shares of convertible preferred stock, and the superior rights and preferences of securities senior to the Company’s common stock at the time.
Initial Public Offering	Initial Public Offering On December 23, 2014, the Company closed its initial public offering (“IPO”) and issued and sold 12,676,354 shares of common stock (inclusive of 1,653,437 shares of common stock sold by the Company pursuant to the full exercise of the underwriters’ option to purchase additional shares) at a price to the public of $24.00 per share. The shares began trading on The NASDAQ Global Select Market on December 19, 2014. The aggregate net proceeds received by the Company from the offering, net of underwriting discounts and commissions and offering expenses, were $279.7 million. Upon the closing of the IPO, all then-outstanding shares of Company convertible preferred stock converted into 59,909,397 shares of common stock. The related carrying value of $387.7 million was reclassified to common stock and additional paid-in capital. Additionally, the Company amended and restated its certificate of incorporation effective December 23, 2014 to, among other things, change the authorized number of shares of common stock to 495,000,000 shares and the authorized number of shares of preferred stock to 5,000,000 shares.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is comprised of net loss and other comprehensive income or loss. Other comprehensive income or loss consists of unrealized gains and losses on marketable securities and foreign currency translation adjustments.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments with original maturities of three months or less at acquisition to be cash equivalents. Cash equivalents, which consist primarily of money market funds, are stated at fair value.
Marketable Securities	Marketable Securities The Company generally invests its excess cash in investment grade short- to intermediate-term fixed income securities. Such investments are included in cash and cash equivalents, marketable securities, or long-term marketable securities on the balance sheets, classified as available-for-sale, and reported at fair value with unrealized gains and losses included in accumulated other comprehensive income (loss). Realized gains and losses on the sale of these securities are recognized in net income or loss. The cost of marketable securities sold is based on the specific identification method. The Company periodically evaluates whether declines in fair values of its investments below their book value are other-than-temporary. This evaluation consists of several qualitative and quantitative factors regarding the severity and duration of the unrealized loss as well as the Company’s ability and intent to hold the investment until a forecasted recovery occurs. Additionally, the Company assesses whether it has plans to sell the security or it is more likely than not it will be required to sell any investment before recovery of its amortized cost basis. Factors considered include quoted market prices, recent financial results and operating trends, implied values from any recent transactions or offers of investee securities, credit quality of debt instrument issuers, other publicly available information that may affect the value of the investments, duration and severity of the decline in value, and our strategy and intentions for holding the investment.
Property and Equipment, Net	Property and Equipment, Net Property and equipment primarily consists of laboratory equipment, computer equipment and software, leasehold improvements and build-to-suit property. Property and equipment is stated at cost, and depreciated using the straight-line method over the estimated useful lives of the respective assets. Laboratory equipment 5 years Computer equipment and software 3 years Leasehold improvements Shorter of asset’s useful life or remaining term of lease
Build-to-Suit Lease Accounting	Build-to-Suit Lease Accounting In February 2015, the Company entered into a lease for a manufacturing facility, which commenced in March 2015. The Company is responsible for the leasehold improvements required to remodel the facility and it bore the majority of the construction risk. Financial Accounting Standards Board (“FASB”) Accounting Standard Codification (“ASC”) 840-40, Leases—Sale-Leaseback Transactions (Subsection 05-5) Construction was completed in the first quarter of 2016, and the Company considered the requirements for sale-leaseback accounting treatment, including evaluating whether all risks of ownership have transferred back to the landlord, as evidenced by a lack of continuing involvement in the leased property. The Company determined that the arrangement does not qualify for sale-leaseback accounting treatment and the building asset will remain on its balance sheet at its historical cost, and such asset will be depreciated over its estimated useful life. The Company bifurcates the lease payments into a portion allocated to the building and a portion allocated to the parcel of land on which the building has been built. The portion of the lease payments allocated to the land is treated for accounting purposes as operating lease payments, and therefore is recorded as rent expense in the statements of operations. The portion of the lease payments allocated to the building is further bifurcated into a portion allocated to interest expense and a portion allocated to reduce the build-to-suit lease obligation. The interest rate used for the build-to-suit lease obligation represents the Company’s estimated incremental borrowing rate, adjusted to reduce any built in loss.
Other Assets	Other Assets Prior to the acquisition of Stage in May 2015, the Company accounted for its minority interest investment in Stage using the cost method in accordance with ASC 325-20, Cost Method Investments
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company regularly reviews the carrying value and estimated lives of its long-lived assets, including property and equipment, to determine whether indicators of impairment may exist which warrant adjustments to carrying values or estimated useful lives. The determinants used for this evaluation include management’s estimate of the asset’s ability to generate positive income from operations and positive cash flow in future periods as well as the strategic significance of the asset to the Company’s business objectives. Should an impairment exist, the impairment loss would be measured based on the excess of the asset’s carrying amount over its fair value. The Company has not recognized any impairment losses since inception on August 5, 2013.
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill represents the excess of the purchase price over the net amount of identifiable assets acquired and liabilities assumed in a business combination measured at fair value. The Company evaluates goodwill for impairment annually during the fourth quarter and upon the occurrence of triggering events or substantive changes in circumstances that could indicate a potential impairment by assessing qualitative factors or performing a quantitative analysis in determining whether it is more likely than not that the fair value of the net assets are below their carrying amounts. Intangible assets acquired in a business combination are recognized separately from goodwill and are initially recognized at their fair value at the acquisition date (which is regarded as their cost). Intangible assets related to in-process research and development (“IPR&D”) are treated as indefinite-lived intangible assets and not amortized until they become definite lived assets upon certain regulatory approval in specified markets, typically either the U.S. or the EU in the case of X-Body, and in the case of Stage, when the acquired reagents or automation technology is accepted by the FDA as part of an Investigational New Drug (“IND”) filing, subject to management judgment. At that time, the Company will determine the useful life of the asset, reclassify the asset out of IPR&D and begin amortization. Intangible assets are reviewed for impairment at least annually or if indicators of potential impairment exist.
Contingent Consideration from Business Combinations	Contingent Consideration from Business Combinations At and subsequent to the acquisition date of a business combination, contingent consideration obligations are remeasured to fair value at each balance sheet date with changes in fair value recognized in research and development expense in the consolidated statements of operations. Changes in fair values reflect changes to the Company’s assumptions regarding probabilities of successful achievement of related milestones, the timing in which the milestones are expected to be achieved, and the discount rate used to estimate the fair value of the obligation, as well as the foreign currency impact of the contingent consideration for the Stage acquisition as it is denominated in Euro.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of the investment credit quality. The hierarchy defines three levels of valuation inputs: Level 1—Quoted prices in active markets for identical assets or liabilities Level 2—Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly Level 3—Unobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability The Company’s financial instruments, in addition to those presented in Note 6, Fair Value Measurements, include cash and cash equivalents, accounts payable, and accrued liabilities. The carrying amount of cash and cash equivalents, accounts payable and accrued liabilities approximate fair value because of the short-term nature of these instruments.
Convertible Preferred Stock Option	Convertible Preferred Stock Option Pursuant to certain 2013 and 2014 convertible preferred stock purchase agreements, the Company had the right to sell, or “put,” additional shares of Series A and A-2 convertible preferred stock in subsequent closings as well as potential obligations to issue additional shares upon the occurrence of certain events. The Company assessed its rights and potential obligations to sell additional shares and determined them to be a single unit of accounting, with classification outside of equity in accordance with ASC 480, Distinguishing Liabilities from Equity The Company recorded these combined instruments as convertible preferred stock options as of the date of the initial closings of the Series A convertible preferred stock financing and Series A-2 convertible preferred stock financing. The options were revalued to fair value at each subsequent balance sheet date, with fair value changes recognized as increases or reductions to other income (expense), net in the consolidated statements of operations. The Company estimated the fair value of these instruments based on the Black-Scholes option pricing model. These options were exercised during 2014. For the year ended December 31, 2014, $10.7 million was recognized in other expense related to the changes in fair value of these options.
Deemed Dividends upon Issuance of Convertible Preferred Stock, Non-Cash	Deemed Dividends upon Issuance of Convertible Preferred Stock, Non-Cash As of the dates of the second tranche closing and third tranche closing of the Series A-2 convertible preferred stock financing in June and July 2014, the estimated fair value of the Series A-2 convertible preferred stock was $5.96 and $7.88 per share, respectively, compared with the purchase price per share of $4.00. As of the date of the final closing of the Series A convertible preferred stock financing in July 2014, the estimated fair value of the Series A convertible preferred stock was $8.36 per share compared with the purchase price per share of $4.00. The differences between the estimated fair value as of the closing dates and the purchase prices were deemed to be equivalent to a preferred stock dividend. As a result, the Company recorded deemed dividends of $15.4 million, $30.3 million, and $21.8 million for the Series A-2 second tranche closing, Series A-2 third tranche closing, and Series A final closing, respectively, in the year ended December 31, 2014. The deemed dividends increased convertible preferred stock by $67.5 million, reduced additional paid-in capital by $16.4 million, and increased accumulated deficit by $51.1 million. The deemed dividends increased the net loss attributable to common stockholders by $67.5 million in the calculation of basic and diluted net loss per common share for the year ended December 31, 2014.
Success Payments	Success Payments The Company granted rights to share-based success payments to the Fred Hutchinson Cancer Research Center (“FHCRC”) and the Memorial Sloan Kettering Cancer Center (“MSK”) pursuant to the terms of its collaboration agreements with each of those entities. Pursuant to the terms of these arrangements, the Company may be required to make success payments based on increases in the per share fair market value of the Company’s common stock, payable in cash or publicly-traded equity at the Company’s discretion. See Note 4, Collaboration and License Agreements. The success payments are accounted for under ASC 505-50, Equity-Based Payments to Non-Employees Derivatives and Hedging Success payment liabilities are estimated at fair value at inception and at each subsequent balance sheet date and the expense is amortized using the accelerated attribution method over the remaining term (service period) of the related collaboration agreement or related possible payment due date (whichever is sooner). To determine the estimated fair value of the success payments the Company uses a Monte Carlo simulation methodology which models the future movement of stock prices based on several key variables. The following variables were incorporated in the estimated fair value of the success payment liability: estimated term of the success payments, fair value of common stock, expected volatility, risk-free interest rate, estimated number and timing of valuation measurement dates on the basis of which payments may be triggered, and certain estimated indirect costs creditable against the success payments are also included in the calculation. The computation of expected volatility was estimated using a combination of available information about the historical volatility of stocks of similar publicly-traded companies for a period matching the expected term assumption and its historical and projected volatility. In addition, prior to the Company becoming publicly traded there was one valuation measurement date on the basis of which payments may be triggered. There are several valuation measurement dates subsequent to the IPO on the basis of which payments may be triggered. In December 2015, success payments to FHCRC were triggered in the aggregate amount of $75.0 million, less indirect cost offsets of $3.3 million. The Company elected to make the payment in shares of the Company’s common stock, and thereby issued 1,601,085 shares of common stock to FHCRC in December 2015. In December 2015, a success payment to MSK was triggered in the amount of $10.0 million, which is required to be paid, less indirect cost offsets that will be determined at the time of payment, in March 2016. As of December 31, 2015 and 2014, the estimated fair value of the success payment obligation after giving effect to the success payments achieved by FHCRC and MSK was approximately $116.2 million and $195.9 million, respectively. The Company recognized research and development expense of $51.6 million and $84.9 million in the year ended December 31, 2015 and 2014, respectively, with respect to the success payment obligations. The success payment liabilities on the consolidated balance sheets as of December 31, 2015 and 2014 were $64.8 million and $84.9 million, respectively. The assumptions used to calculate the fair value of the success payments are subject to a significant amount of judgment including the expected volatility, estimated term, and estimated number and timing of valuation measurement dates. A small change in the assumptions may have a relatively large change in the estimated valuation and associated liability and expense. For example, keeping all other variables constant, a hypothetical 10% increase in the stock price at December 31, 2015 from $43.97 per share to $48.37 per share would have increased the expense recorded in 2015 associated with the success payment liability by $7.7 million. A hypothetical 10% decrease in the stock price from $43.97 per share to $39.57 per share would have decreased the expense recorded in 2015 associated with the success payment liability by $7.6 million. Further, keeping all other variables constant, a hypothetical 35% increase in the stock price at December 31, 2015 from $43.97 per share to $59.36 per share would have increased the expense recorded in 2015 associated with the success payment liability by $27.3 million. A hypothetical 35% decrease in the stock price from $43.97 per share to $28.58 per share would have decreased the expense recorded in 2015 associated with the success payment liability by $25.7 million.
Concentrations of Credit Risk and Off-Balance Sheet Risk	Concentrations of Credit Risk and Off-Balance Sheet Risk The Company maintains its cash, cash equivalents, and marketable securities with high quality, accredited financial institutions. These amounts at times may exceed federally insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to significant risk on these funds. The Company has no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements.
Revenue	Revenue The Company recognizes revenue for each unit of accounting when all of the following criteria are met: • persuasive evidence of an arrangement exists; • delivery has occurred or services have been rendered; • the seller’s price to the buyer is fixed or determinable; and • collectability is reasonably assured. Amounts received prior to satisfying the revenue recognition criteria are recorded as deferred revenue in the Company’s consolidated balance sheets. Amounts expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue in current liabilities. Amounts not expected to be recognized as revenue within the 12 months following the balance sheet date are classified as deferred revenue, less current portion. The Company analyzes agreements with more than one element, or deliverable, based on the guidance in ASC 605-25, Revenue Recognition-Multiple-Element Arrangements (“ASC 605-25”). The Company identifies the deliverables within the agreement and evaluates which deliverables represent separate units of accounting. Analyzing the agreement to identify deliverables requires the use of judgment. A deliverable is considered a separate unit of accounting when the deliverable has value to the collaborator or licensee on a standalone basis based on the consideration of the relevant facts and circumstances for each agreement. In assessing whether an item has standalone value, the Company considers factors such as the research, manufacturing, and commercialization capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the other deliverable(s) can be used for their intended purpose without the receipt of the remaining element(s), whether the value of the deliverable is dependent on the undelivered item(s) and whether there are other vendors that can provide the undelivered element(s). Consideration received is allocated at the inception of the agreement to all identified units of accounting based on the relative selling prices. The relative selling price for each deliverable is estimated using objective evidence if it is available. If objective evidence is not available, the Company uses its best estimate of the selling price for the deliverable. Management may be required to exercise considerable judgment in estimating the selling prices of identified units of accounting under its agreements. Options for future deliverables are considered substantive if, at the inception of the arrangement, the Company is at risk as to whether the collaboration partner will choose to exercise the option. Factors that the Company considers in evaluating whether an option is substantive include the overall objective of the arrangement, the benefit the collaborator might obtain from the arrangement without exercising the option, the cost to exercise the option and the likelihood that the option will be exercised. For arrangements under which an option is considered substantive, the Company does not consider the item underlying the option to be a deliverable at the inception of the arrangement and the associated option fees are not included in the initial consideration, assuming the option is not priced at a significant and incremental discount. Conversely, for arrangements under which an option is not considered substantive or if an option is priced at a significant and incremental discount, the Company would consider the item underlying the option to be a deliverable at the inception of the arrangement and a corresponding amount would be included in the initial consideration. The consideration received is allocated among the separate units of accounting, and the applicable revenue recognition criteria are applied to each of the separate units. The Company recognizes the revenue allocated to each unit of accounting over the period of performance. Revenue is recognized using either a proportional performance or straight-line method, depending on whether the Company can reasonably estimate the level of effort required to complete its performance obligations under an arrangement.
Research and Development Expense	Research and Development Expense The Company records expense for research and development costs to operations as incurred. For service contracts entered into that include a nonrefundable prepayment for service, the upfront payment is deferred and recognized in the statement of operations as the services are rendered. Research and development expenses consist of costs incurred by the Company for the discovery and development of the Company’s product candidates and include: • Clinical trial costs; • external research and development expenses incurred under arrangements with third parties, such as contract research organizations, contract manufacturing organizations, academic and non-profit institutions and consultants; • costs incurred in connection with preclinical development activities; • costs to acquire complimentary technology; • personnel-related expenses, including non-cash stock-based compensation expense; • changes in the estimated fair value of the liability attributable to the elapsed service period as of the balance sheet date associated with the Company’s success payments to FHCRC and MSK; • changes in the estimated fair value of the contingent consideration liabilities; • license fees; and • other expenses, which include direct and allocated expenses for laboratory, facilities, and other costs.
General and Administrative Expense	General and Administrative Expense General and administrative costs are expensed as incurred and include personnel-related expenses including non-cash stock-based compensation for our personnel in executive, legal, finance and accounting, and other administrative functions, legal costs other than litigation expense associated with Trustees of the University of Pennsylvania v. St. Jude Children’s Research Hospital
Litigation Expense	Litigation Expense Litigation expense includes legal expense the Company incurred with respect to Trustees of the University of Pennsylvania v. St. Jude Children’s Research Hospital
Stock-Based Compensation	Stock-Based Compensation Under ASC 718, Compensation—Stock Compensation, • the expected term of the option, which is calculated using the simplified method, as permitted by the Securities and Exchange Commission (“SEC”) Staff Accounting Bulletin No. 110, Share-Based Payment, as the Company has insufficient historical information regarding its stock options to provide a basis for an estimate; • the expected volatility of the underlying common stock, which the Company estimates based on the historical volatility of a representative group of publicly traded biopharmaceutical companies with similar characteristics, and the Company’s own historical and implied future volatility; • the risk-free interest rate, which is based on the yield curve of U.S. Treasury securities with periods commensurate with the expected term of the options being valued; • the expected dividend yield, which the Company estimates to be zero based on the fact that the Company has never paid cash dividends and has no present intention to pay cash dividends; and • the fair value of the Company’s common stock on the date of grant. Stock-based compensation expense for restricted stock, RSUs, and stock options is recognized on a straight-line basis over the requisite service period, which is generally the vesting period of the respective award. The Company is required to estimate a forfeiture rate to calculate the stock-based compensation expense for its awards. The Company’s forfeiture rate is based on an analysis of its actual forfeitures since the adoption of its equity award plan. Since inception the Company’s estimated forfeiture rate has been de minimis The Company also granted restricted stock awards that vest in conjunction with certain performance conditions to certain key employees, scientific founders, and directors. At each reporting date, the Company is required to evaluate whether achievement of the performance conditions is probable. Compensation expense is recorded over the appropriate service period based upon the Company’s assessment of accomplishing each performance provision. Compensation expense is measured using the fair value of the award at the grant date, net of forfeitures, and is adjusted annually to reflect actual forfeitures. The Company also grants stock-based awards to certain service providers who are not employees, scientific founders, or directors. Stock-based awards issued to such persons, or to directors for non-board related services, are accounted for based on the fair value of such services received or of the equity instruments issued, whichever is more reliably measured. The fair value of such awards is subject to remeasurement at each reporting period until services required under the arrangement are completed, which is the vesting date.
Patent Costs	Patent Costs The costs related to acquiring patents and to prosecuting and maintaining intellectual property rights are expensed as incurred to general and administrative due to the uncertainty surrounding the drug development process and the uncertainty of future benefits.
Income Taxes	Income Taxes The Company determines its deferred tax assets and liabilities based on the differences between the financial reporting and tax basis of assets and liabilities. The deferred tax assets and liabilities are measured using the enacted tax rates that will be in effect when the differences are expected to reverse. A valuation allowance is recorded when it is more likely than not that the deferred tax asset will not be recovered. The Company applies judgment in the determination of the consolidated financial statement recognition and measurement of a tax position taken or expected to be taken in a tax return. The Company recognizes any material interest and penalties related to unrecognized tax benefits in income tax expense. The Company is required to file income tax returns in the U.S. federal jurisdiction and various state and foreign jurisdictions. The Company currently is not under examination by the Internal Revenue Service or other jurisdictions for any tax years.
Foreign Currency Translation	Foreign Currency Translation Assets and liabilities denominated in foreign currencies were translated into U.S. dollars, the reporting currency, at the exchange rate prevailing at the balance sheet date. Revenue and expenses denominated in foreign currencies were translated into U.S. dollars at the monthly average exchange rate for the period and the translation adjustments are reported as an element of accumulated other comprehensive income or loss on the consolidated balance sheets.
Net Loss per Share Attributable to Common Stockholders	Net Loss per Share Attributable to Common Stockholders Basic and diluted net loss per share attributable to common stockholders is calculated by dividing net loss attributable to common stockholders by the weighted average number of common shares outstanding during the period, without consideration for common stock equivalents. The Company’s potentially dilutive shares, which include unvested restricted stock, unvested RSUs, options to purchase common stock, and potential shares issued for success payments, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. The following table reconciles net loss to net loss attributable to common stockholders (in thousands, except share and per share data): Year Ended December 31, Period from December 31, 2013 2015 2014 Net loss $ (239,376 ) $ (243,407 ) $ (51,820 ) Deemed dividend upon issuance of convertible preferred stock — (67,464 ) — Net loss attributable to common stockholders $ (239,376 ) $ (310,871 ) $ (51,820 ) Weighted average number of common shares used in net loss per share attributable to common stockholders—basic and diluted 88,145,424 8,442,947 3,658,687 Net loss per share attributable to common stockholders—basic and diluted $ (2.72 ) $ (36.82 ) $ (14.16 ) The amounts in the table below were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated due to their anti-dilutive effect: Year Ended December 31, Period from December 31, 2013 2015 2014 Series A convertible preferred stock — — 16,930,664 Series A-1 convertible preferred stock — — 2,250,000 Unvested restricted common stock and restricted stock units 5,476,600 8,352,714 5,789,123 Options to purchase common stock 5,218,939 2,720,351 — Estimated number of shares issued for success payments 204,527 1 1,627,729 2 — Total 10,900,066 12,700,794 24,969,787 (1) In December 2015 a success payment to MSK was triggered in the amount of $10.0 million, less certain indirect cost offsets that will be determined at the time of payment in March 2016. This represents the number of shares that would have been issued if the success payment to MSK had been made on December 31, 2015 had we chosen to pay this obligation by issuing stock. The number of shares issued for purposes of this presentation is calculated by dividing the success payment by the closing stock price per share on December 31, 2015. The actual number of shares to be issued, if we choose to pay the obligation by issuing stock, will be calculated by dividing the success payment achieved by the volume weighted average trading price of the Company’s common stock on March 17, 2016. (2) Represents the number of shares that would have been issued if the success payment valuation date had been December 31, 2014. The Company’s common stock closing price per share was $52.22 at December 31, 2014 which value if used for purposes of determining what success payments were triggered would have resulted in a success payment of $85.0 million ($75.0 million for FHCRC and $10.0 million for MSK). The number of shares issued for purposes of this presentation is calculated by dividing the success payment by the closing stock price per share at December 31, 2014.
Segments	Segments Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment and one reportable segment.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In November 2015, the FASB issued Accounting Standards Update (“ASU”) No. 2015-17, Balance Sheet Classification of Deferred Taxes (Topic 740) In 2014, the FASB issued new accounting guidance related to revenue recognition. This new standard will replace all current GAAP guidance on this topic and establishes principles for recognizing revenue upon the transfer of promised goods or services to customers, in an amount that reflects the expected consideration received in exchange for those goods or services. This guidance can be applied either retrospectively to each period presented or as a cumulative-effect adjustment as of the date of adoption. In July 2015, the FASB voted to defer the effective date to January 1, 2018 with early adoption permitted beginning January 1, 2017. The Company is evaluating the impact of adopting the new accounting guidance on its consolidated financial statements.

Significant Accounting Polici28

Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Schedule of Estimated Useful Lives of Property and Equipment	Property and equipment is stated at cost, and depreciated using the straight-line method over the estimated useful lives of the respective assets. Laboratory equipment 5 years Computer equipment and software 3 years Leasehold improvements Shorter of asset’s useful life or remaining term of lease
Reconciliation of Net Loss to Net Loss Attributable to Common Stockholders	The following table reconciles net loss to net loss attributable to common stockholders (in thousands, except share and per share data): Year Ended December 31, Period from December 31, 2013 2015 2014 Net loss $ (239,376 ) $ (243,407 ) $ (51,820 ) Deemed dividend upon issuance of convertible preferred stock — (67,464 ) — Net loss attributable to common stockholders $ (239,376 ) $ (310,871 ) $ (51,820 ) Weighted average number of common shares used in net loss per share attributable to common stockholders—basic and diluted 88,145,424 8,442,947 3,658,687 Net loss per share attributable to common stockholders—basic and diluted
Schedule of Diluted Net Loss Per Share Attributable to Common Stockholders Due to Anti-Dilutive Effect	The amounts in the table below were excluded from the calculation of diluted net loss per share attributable to common stockholders for the periods indicated due to their anti-dilutive effect: Year Ended December 31, Period from December 31, 2013 2015 2014 Series A convertible preferred stock — — 16,930,664 Series A-1 convertible preferred stock — — 2,250,000 Unvested restricted common stock and restricted stock units 5,476,600 8,352,714 5,789,123 Options to purchase common stock 5,218,939 2,720,351 — Estimated number of shares issued for success payments 204,527 1 1,627,729 2 — Total 10,900,066 12,700,794 24,969,787 (1) In December 2015 a success payment to MSK was triggered in the amount of $10.0 million, less certain indirect cost offsets that will be determined at the time of payment in March 2016. This represents the number of shares that would have been issued if the success payment to MSK had been made on December 31, 2015 had we chosen to pay this obligation by issuing stock. The number of shares issued for purposes of this presentation is calculated by dividing the success payment by the closing stock price per share on December 31, 2015. The actual number of shares to be issued, if we choose to pay the obligation by issuing stock, will be calculated by dividing the success payment achieved by the volume weighted average trading price of the Company’s common stock on March 17, 2016. (2) Represents the number of shares that would have been issued if the success payment valuation date had been December 31, 2014. The Company’s common stock closing price per share was $52.22 at December 31, 2014 which value if used for purposes of determining what success payments were triggered would have resulted in a success payment of $85.0 million ($75.0 million for FHCRC and $10.0 million for MSK). The number of shares issued for purposes of this presentation is calculated by dividing the success payment by the closing stock price per share at December 31, 2014.

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2015
Summary of Changes in Carrying Amount of Goodwill	The following table summarizes the changes in the carrying amount of goodwill (in thousands): Balance at December 31, 2014 $ — Goodwill acquired 122,092 Balance at December 31, 2015 $ 122,092
Summary of Gross Carrying Amount, Accumulated Amortization and Net Carrying Amount of Intangible Assets	The following table summarizes the gross carrying amount, accumulated amortization and the net carrying amount of intangible assets (in thousands): December 31, 2015 Gross Carrying Accumulated Intangible Acquired in-process research and development $ 50,177 $ — $ 50,177 Total intangible assets $ 50,177 $ — $ 50,177
Stage Cell Therapeutics GmbH [Member]
Schedule of Purchase Consideration	The elements of the purchase consideration are as follows (in thousands): Cash paid (1) $ 58,496 Common stock issued (2) 22,165 Fair value of contingent consideration (3) 28,244 Total consideration for 95.24% equity 108,905 Fair value of 4.76% initial investment in Stage (4) 3,682 Implied purchase price consideration for 100% equity $ 112,587 (1) The cash consideration represents the consideration paid in cash amounting to €52.5 million which is translated based on an exchange rate on May 11, 2015. (2) Based on the share purchase agreement, the purchase consideration included 486,279 shares of the Company’s common stock. The closing stock price on the transaction date was $45.58 per share. (3) The fair value of the contingent consideration was determined by calculating the probability-weighted milestone payments based on the assessment of the likelihood and estimated timing that certain milestones would be achieved. The fair value of the contingent consideration was estimated using a discount rate of 14.6%. The discount rate captures the credit risk associated with the payment of the contingent consideration when earned and due. (4) The fair value of the initial investment is calculated as the implied per share fair value of the stock based upon the acquisition purchase price reduced by a lack of control discount associated with the 4.76% holding. Upon acquiring the remaining outstanding ownership interests in Stage, the Company remeasured its original equity interest to its fair value and recognized a $0.2 million gain during the year ended December 31, 2015, which was recorded in other income (expense) on the consolidated statements of operations.
Components of Purchase Price Allocation	The components of the purchase price allocation are as follows (in thousands): Net working capital $ 1,863 Property and equipment 651 Net assets acquired 2,514 Deferred tax liabilities (10,801 ) Acquired in-process research and development 34,457 Goodwill 86,417 Total consideration transferred $ 112,587
X- BODY [Member]
Schedule of Purchase Consideration	The elements of the purchase consideration are as follows (in thousands): Cash paid $ 21,331 Common stock issued (1) 19,447 Fair value of contingent consideration (2) 8,944 Settlement of preexisting obligation (3) 1,123 Total consideration $ 50,845 (1) Based on the share purchase agreement, the purchase consideration included 366,434 shares of the Company’s common stock. The closing stock price on the transaction date was $53.07 per share. (2) The fair value of the contingent consideration was determined by calculating the probability-weighted milestone based on the assessment of the likelihood and estimated timing that certain milestones would be achieved. The fair value of the contingent consideration was estimated using a discount rate of 15.2%. The discount rate captures the credit risk associated with the payment of the contingent consideration when earned and due. (3) The settlement of preexisting obligation reflects the effective settlement of the Company’s preexisting prepaid contract research agreement with X-Body. No gain or loss was recognized by the Company on the effective settlement of this prepaid expense as of the acquisition date.
Components of Purchase Price Allocation	The components of the purchase price allocation are as follows (in thousands): Net liabilities assumed $ (181 ) Deferred tax liabilities (1,099 ) Acquired in-process research and development 16,450 Goodwill 35,675 Total consideration transferred $ 50,845

Collaboration and License Agr30

Collaboration and License Agreements (Tables)	12 Months Ended
	Dec. 31, 2015
Fred Hutchinson Cancer Research Center [Member]
Summary of All Possible FHCRC Success Payments, Payable in Cash or Publicly-Traded Equity	The following table summarizes all possible FHCRC success payments, which are payable in cash or publicly-traded equity at the Company’s discretion: Multiple of Initial Equity Value at issuance 5.0x 7.5x 10.0x 15.0x 20.0x 25.0x 30.0x 35.0x 40.0x Per share common stock price required for payment $ 20.00 $ 30.00 $ 40.00 $ 60.00 $ 80.00 $ 100.00 $ 120.00 $ 140.00 $ 160.00 Success payment(s) (in millions) $ 10 $ 25 $ 40 $ 50 $ 50 $ 50 $ 50 $ 50 $ 50
Assumptions Used to Calculate Estimated Fair Value of Success Payment Liability	The following variables were incorporated in the calculation of the estimated fair value of the success payment liability as of the following balance sheet dates: December 31, Assumptions 2015 2014 Fair value of common stock $ 43.97 $ 52.22 Risk free interest rate 1.89% – 2.20 % 1.94% – 2.16 % Expected volatility 70 % 75 % Expected term (years) 5.79 – 8.79 6.79 – 9.79
Memorial Sloan Kettering Cancer Center [Member]
Summary of All Possible FHCRC Success Payments, Payable in Cash or Publicly-Traded Equity	The following table summarizes all possible MSK success payments, which are payable in cash or publicly-traded equity at the Company’s discretion: Multiple of Initial Equity Value at issuance 10.0x 15.0x 30.0x Per share common stock price required for payment $ 40.00 $ 60.00 $ 120.00 Success payment(s) (in millions) $ 10 $ 70 $ 70
Assumptions Used to Calculate Estimated Fair Value of Success Payment Liability	The following variables were incorporated in the calculation of the estimated fair value of the success payment liability as of the following balance sheet dates: December 31, Assumptions 2015 2014 Fair value of common stock $ 43.97 $ 52.22 Risk free interest rate 1.91% – 2.20 % 1.95% – 2.16 % Expected volatility 70 % 75 % Expected term (years) 5.89 – 8.89 6.89 – 9.89

Cash Equivalents and Marketab31

Cash Equivalents and Marketable Securities (Tables)	12 Months Ended
	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Summary of Estimated Fair Value of Cash Equivalents and Marketable Securities	The following tables summarize the estimated fair value of our cash equivalents and marketable securities and the gross unrealized holding gains and losses (in thousands): December 31, 2015 Amortized Gross Gross Estimated Fair Cash equivalents: Money market funds $ 177,164 $ — $ — $ 177,164 Commercial paper 45,352 — — 45,352 U.S. government and agency securities 2,000 — — 2,000 Corporate debt securities 5,040 — — 5,040 Total cash equivalents 229,556 — — 229,556 Marketable securities: Commercial paper 73,078 — — 73,078 U.S. government and agency securities 470,519 2 (485 ) 470,036 Corporate debt securities 148,143 1 (245 ) 147,899 Total marketable securities 691,740 3 (730 ) 691,013 Long-term marketable securities: U.S. government and agency securities 204,551 1 (770 ) 203,782 Corporate debt securities 65,898 33 (195 ) 65,736 Equity securities 7,190 — (3,820 ) 3,370 Total long-term marketable securities $ 277,639 $ 34 $ (4,785 ) $ 272,888 December 31, 2014 Amortized Gross Unrealized Gross Unrealized Estimated Fair Cash equivalents: Money market funds $ 223,745 $ — $ — $ 223,745 Commercial paper 13,294 — — 13,294 U.S. government and agency securities 7,582 — — 7,582 Corporate debt securities 1,702 — — 1,702 Total cash equivalents 246,323 — — 246,323 Marketable securities: Commercial paper 1,999 — — 1,999 U.S. government and agency securities 47,868 — (21 ) 47,847 Corporate debt securities 29,863 — (37 ) 29,826 Total marketable securities 79,730 — (58 ) 79,672 Long-term marketable securities: U.S. government and agency securities 34,898 — (25 ) 34,873 Corporate debt securities 3,544 1 (7 ) 3,538 Total long-term marketable securities $ 38,442 $ 1 $ (32 ) $ 38,411
Summary of Gross Unrealized Holding Losses and Fair Value for Investments in Unrealized Loss Position	The following tables summarize the gross unrealized holding losses and fair value for investments in an unrealized loss position, and the length of time that individual securities have been in a continuous loss position (in thousands): December 31, 2015 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Marketable securities: U.S. government and agency securities $ 457,641 $ (485 ) $ — $ — $ 457,641 $ (485 ) Corporate debt securities 144,499 (245 ) — — 144,499 (245 ) Total marketable securities 602,140 (730 ) — — 602,140 (730 ) Long-term marketable securities: U.S. government and agency securities 190,767 (770 ) — — 190,767 (770 ) Corporate debt securities 50,591 (195 ) — — 50,591 (195 ) Equity securities 3,370 (3,820 ) — — 3,370 (3,820 ) Total long-term marketable securities $ 244,728 $ (4,785 ) $ — $ — $ 244,728 $ (4,785 ) December 31, 2014 Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Fair Value Unrealized Fair Value Unrealized Marketable securities: U.S. government and agency securities $ 43,332 $ (21 ) $ — $ — $ 43,332 $ (21 ) Corporate debt securities 26,611 (37 ) — — 26,611 (37 ) Total marketable securities 69,943 (58 ) — — 69,943 (58 ) Long-term marketable securities: U.S. government and agency securities 33,873 (25 ) — — 33,873 (25 ) Corporate debt securities 2,003 (7 ) — — 2,003 (7 ) Total long-term marketable securities $ 35,876 $ (32 ) $ — $ — $ 35,876 $ (32 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis	The following tables set forth the fair value of the Company’s financial assets and liabilities measured at fair value on a recurring basis based on the three-tier fair value hierarchy (in thousands): December 31, 2015 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 177,164 $ — $ — $ 177,164 Commercial paper — 118,430 — 118,430 U.S. government and agency securities — 675,818 — 675,818 Corporate debt securities — 218,675 — 218,675 Equity securities 3,370 — — 3,370 Total financial assets $ 180,534 $ 1,012,923 $ — $ 1,193,457 Financial Liabilities: Success payment liabilities $ — $ — $ 64,829 $ 64,829 Contingent consideration — — 37,266 37,266 Total financial liabilities $ — $ — $ 102,095 $ 102,095 December 31, 2014 Level 1 Level 2 Level 3 Total Financial Assets: Money market funds $ 223,745 $ — $ — $ 223,745 Commercial paper — 15,293 — 15,293 U.S. government and agency securities — 90,302 — 90,302 Corporate debt securities — 35,066 — 35,066 Total financial assets $ 223,745 $ 140,661 $ — $ 364,406 Financial Liabilities: Success payment liabilities $ — $ — $ 84,920 $ 84,920 Total financial liabilities $ — $ — $ 84,920 $ 84,920
Summary of Changes in Fair Value of Level 3 Financial Liabilities	The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands): Success Contingent Total Balance at December 31, 2013 $ — $ — $ — Additions — — — Changes in fair value (1) 84,920 — 84,920 Balance at December 31, 2014 84,920 — 84,920 Additions — 37,188 37,188 Payments (71,648 ) — (71,648 ) Changes in fair value (1) 51,557 78 51,635 Balance at December 31, 2015 $ 64,829 $ 37,266 $ 102,095 (1) The amount of success payments achieved and changes in fair value for success payment liabilities and contingent consideration are recorded in research and development expense in the consolidated statements of operations.

Property and Equipment, Net (Ta

Property and Equipment, Net (Tables)	12 Months Ended
	Dec. 31, 2015
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment, Net	Property and equipment, net consisted of the following (in thousands): December 31, 2015 2014 Construction in progress $ 23,214 $ — Build-to-suit asset 9,910 — Laboratory equipment 9,706 3,921 Computer equipment, software and other 773 198 Leasehold improvements 300 98 Property and equipment, at cost 43,903 4,217 Less: Accumulated depreciation (1,817 ) (199 ) Property and equipment, net $ 42,086 $ 4,018

Accrued Liabilities and Other34

Accrued Liabilities and Other Current Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Payables and Accruals [Abstract]
Schedule of Accrued Liabilities and Other Current Liabilities	Accrued liabilities and other current liabilities consisted of the following (in thousands): December 31, 2015 2014 Accrued clinical expenses $ 7,174 $ 564 Accrued research and development expenses 7,132 2,724 Accrued bonus expense 7,054 3,106 Accrued employee expenses 3,281 531 Accrued milestones 2,827 — Accrued legal expenses 1,987 4,309 Accrued offering costs — 1,456 Other 3,921 1,887 Total accrued liabilities and other current liabilities $ 33,376 $ 14,577

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock-Based Compensation Expense	Stock-based compensation expense is recognized in our consolidated statements of operations as follows (in thousands): Year Ended December 31, Period from December 31, 2013 2015 2014 Research and development $ 17,089 $ 2,908 $ 125 General and administrative 14,852 3,596 — Total stock-based compensation expense (1) $ 31,941 $ 6,504 $ 125 (1) Included in stock-based compensation expense recognized for the years ended December 31, 2015 and 2014, is $8.1 million and $2.8 million, respectively, related to service providers other than our employees, scientific founders, and directors, including $6.2 million and $2.5 million, respectively, for a former co-founding director who became a consultant upon his departure from the board of directors.
Summary of Restricted Stock and RSU Activity	A summary of the Company’s restricted stock and RSU activity is as follows: Shares Weighted Average Fair Unvested shares as of December 31, 2014 8,352,714 $ 1.46 Granted 395,987 49.51 Vested (3,245,512 ) 0.51 Forfeited (26,589 ) 0.60 Unvested shares as of December 31, 2015 5,476,600 $ 3.72
Summary of Stock Option Activity	A summary of the Company’s stock option activity is as follows: Number of Weighted Weighted Aggregate Outstanding as of December 31, 2014 2,720,351 $ 7.23 Granted 2,914,406 49.08 Exercised (268,765 ) 7.39 Cancelled (147,053 ) 19.20 Outstanding as of December 31, 2015 5,218,939 $ 30.25 9.13 $ 86,609 Exercisable as of December 31, 2015 806,477 $ 16.17 8.70 $ 23,160
Summary of Material Factors Incorporated in Black-Scholes Model in Estimating Fair Value of Options Granted to Employees and Consultants	The fair value of each stock option granted has been determined using the Black-Scholes option pricing model. The material factors incorporated in the Black-Scholes model in estimating the fair value of the options granted to employees, directors, and consultants included the following: December 31, Assumptions 2015 2014 Risk free interest rate 1.53% – 2.35 % 1.59% – 2.17 % Expected volatility 70% – 80 % 75 % Expected life (years) 6.02 – 10 6.25 – 10 Expected dividend yield 0 % 0 %

Accumulated Other Comprehensi36

Accumulated Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Dec. 31, 2015
Equity [Abstract]
Components of Accumulated Other Comprehensive Income (Loss) and Adjustments to Other Comprehensive Income (Loss)	The components of accumulated other comprehensive income (loss) and the adjustments to other comprehensive income (loss) are as follows (in thousands): Foreign Currency Net Unrealized Available-For-Sale Accumulated Other Balance at December 31, 2013 $ — $ — $ — Other comprehensive loss — (90 ) (90 ) Balance at December 31, 2014 — (90 ) (90 ) Other comprehensive loss (605 ) (5,388 ) (5,993 ) Balance at December 31, 2015 $ (605 ) $ (5,478 ) $ (6,083 )

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Schedule of Loss Before Income Taxes Attributable to Tax Jurisdictions	Loss before income taxes is attributable to the following tax jurisdictions (in thousands): Year Ended December 31, Period from August 5, 2013 to December 31, 2013 2015 2014 United States $ 236,028 $ 243,407 $ 51,820 Foreign 6,108 — — Loss before income taxes $ 242,136 $ 243,407 $ 51,820
Components of the Benefit for Income Taxes	The components of the benefit for income taxes are as follows (in thousands): Year Ended December 31, Period from August 5, 2013 to December 31, 2013 2015 2014 Deferred: United States $ 1,100 $ — $ — Foreign 1,660 — — Total deferred 2,760 — — Provision for income taxes $ 2,760 $ — $ —
Summary of Income Tax Rate Reconciliation	A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations follows: Year Ended December 31, Period from August 5, 2013 to December 31, 2013 2015 2014 Federal statutory tax 35.0 % 34.0 % 34.0 % Foreign tax rate differential (0.1 ) — — Valuation allowance (36.2 ) (32.4 ) (30.0 ) Tax credits 3.8 0.7 0.2 Other (1.4 ) (2.3 ) (4.2 ) Total 1.1 % 0.0 % 0.0 %
Components of Net Deferred Tax Liabilities	The principal components of the Company’s net deferred tax liabilities are as follows (in thousands): December 31, 2015 2014 Deferred tax assets: Net operating loss carryforwards $ 56,862 $ 17,391 Tax credit carryforwards 14,561 1,799 Acquired technology 57,369 45,534 Success payments 47,745 28,872 Stock compensation 4,342 115 Other 5,019 1,430 Gross deferred tax assets 185,898 95,141 Valuation allowance (183,597 ) (94,368 ) Deferred tax assets, net of valuation allowance 2,301 773 Deferred tax liabilities: Acquired technology (10,540 ) — Other (707 ) (773 ) Deferred tax liabilities (11,247 ) (773 ) Net deferred tax liabilities $ (8,946 ) $ —

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Summary of Company's Future Minimum Lease Commitments	The following table summarizes the Company’s future minimum lease commitments as of December 31, 2015 (in thousands): Year ending December 31: 2016 $ 3,890 2017 4,983 2018 10,652 2019 10,901 2020 11,156 Thereafter 42,031 Total minimum lease payments $ 83,613

Selected Quarterly Financial 39

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	The following table contains quarterly financial information for the years ended December 31, 2015 and 2014. The unaudited quarterly information has been prepared on a basis consistent with the audited consolidated financial statements and includes all adjustments that the Company considers necessary for a fair presentation of the information shown. The operating results for any fiscal quarter are not necessarily indicative of the operating results for a full fiscal year or for any future period and there can be no assurances that any trend reflected in such results will continue in the future. Year Ended December 31, 2015 First Second Third Fourth (In thousands, except per share data) Loss from operations (1) (65,160 ) (67,965 ) (23,533 ) (87,442 ) Net loss (64,965 ) (65,958 ) (23,240 ) (85,213 ) Net loss per share attributable to common stockholders, basic and diluted (0.79 ) (0.79 ) (0.26 ) (0.89 ) Year Ended December 31, 2014 First Second Third Fourth (In thousands, except per share data) Loss from operations (8,320 ) (12,680 ) (19,818 ) (191,940 ) Net loss (8,949 ) (22,769 ) (19,818 ) (191,871 ) Deemed dividends upon issuance of convertible preferred stock — (15,357 ) (52,107 ) — Net loss attributable to common stockholders (8,949 ) (38,126 ) (71,925 ) (191,871 ) Net loss per share attributable to common stockholders, basic and diluted (1.41 ) (5.80 ) (10.50 ) (13.68 ) (1) Included in loss from operations is non-cash expense associated with the success payment liabilities to FHCRC and MSK attributable to the change in value and elapsed service period as follows: Year Ended December 31, 2015 First Second Third Fourth (In thousands) Non-cash succes payment expense (gain) included in loss from operations 38,911 3,961 (25,586 ) 34,273 (2) Included in loss from operations in the second quarter of 2015 is $30.8 million in upfront fees associated with the Editas and Fate collaborations. (3) Included in loss from operations in the fourth quarter of 2014 is $83.4 million associated with the portion of the success payment liability to FHCRC and MSK attributable to the elapsed service period and $84.1 million in upfront fees to acquire technology related to JCAR018, $20.0 million of which was paid in cash and $64.1 million was paid through the issuance of common stock.

Organization and Basis of Prese

Organization and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Organization And Basis Of Presentation [Line Items]
Accumulated deficit	$ (585,657)	$ (346,281)
Stage Cell Therapeutics GmbH [Member]
Organization And Basis Of Presentation [Line Items]
Acquisition date	May 11, 2015
X- BODY [Member]
Organization And Basis Of Presentation [Line Items]
Acquisition date	Jun. 1, 2015

Significant Accounting Polici41

Significant Accounting Policies - Additional Information (Detail)	Dec. 23, 2014USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares	Jul. 31, 2014$ / shares	Jun. 30, 2014$ / shares	Dec. 31, 2015USD ($)$ / sharesshares	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Sep. 30, 2014USD ($)	Jun. 30, 2014USD ($)	Dec. 31, 2015USD ($)Segments$ / sharesshares	Dec. 31, 2014USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares
Schedule Of Accounting Policies [Line Items]
Aggregate net proceeds received from initial public offering	$ 279,700,000
Conversion of preferred stock into common stock, shares | shares	59,909,397
Conversion of preferred stock into common stock	$ 387,700,000											$ 387,695,000
Common stock, shares authorized | shares	495,000,000	495,000,000			495,000,000						495,000,000	495,000,000	495,000,000
Preferred stock, shares authorized | shares	5,000,000	5,000,000			5,000,000						5,000,000	5,000,000	5,000,000
Total investments												$ 3,500,000
Impairment losses											$ 0		$ 0
Decrease in additional paid-in capital by effect of deemed dividends												16,400,000
Increase in accumulated deficit by effect of deemed dividends												51,100,000
Deemed dividend upon issuance of convertible preferred stock, non-cash									$ 52,107,000	$ 15,357,000		67,464,000
Estimated fair value of success payment obligation		$ 116,200,000			$ 116,200,000						116,200,000	195,900,000	116,200,000
Success payment expense					34,273,000	$ (25,586,000)	$ 3,961,000	$ 38,911,000			51,600,000	84,900,000
Success payment liabilities		64,829,000			64,829,000						$ 64,829,000	$ 84,920,000	64,829,000
Expected dividend yield											0.00%	0.00%
Number of operating segments | Segments											1
Number of reportable segments | Segments											1
Fred Hutchinson Cancer Research Center [Member]
Schedule Of Accounting Policies [Line Items]
Success payments paid		75,000,000			$ 75,000,000						$ 75,000,000		$ 75,000,000
Indirect cost related to collaboration agreements		$ 3,300,000
Issuance of common stock for success payments | shares		1,601,085
Stock price per share | $ / shares		$ 43.97			$ 43.97						$ 43.97	$ 52.22	$ 43.97
Memorial Sloan Kettering Cancer Center [Member]
Schedule Of Accounting Policies [Line Items]
Success payments paid		$ 10,000,000			$ 10,000,000						$ 10,000,000		$ 10,000,000
Stock price per share | $ / shares		$ 43.97			$ 43.97						$ 43.97	$ 52.22	$ 43.97
Convertible Preferred Stock Option [Member]
Schedule Of Accounting Policies [Line Items]
Other expense												$ 10,700,000
Series A-2 convertible preferred stock [Member]
Schedule Of Accounting Policies [Line Items]
Estimated fair value upon issuance of convertible preferred stock | $ / shares			$ 7.88	$ 5.96
Purchase price per share | $ / shares			4
Series A convertible preferred stock [Member]
Schedule Of Accounting Policies [Line Items]
Estimated fair value upon issuance of convertible preferred stock | $ / shares			8.36
Purchase price per share | $ / shares			$ 4
Series A-2 Second Tranche Closing [Member]
Schedule Of Accounting Policies [Line Items]
Non-cash deemed dividends on convertible preferred stock												15,400,000
Series A-2 Third Tranche Closing [Member]
Schedule Of Accounting Policies [Line Items]
Non-cash deemed dividends on convertible preferred stock												30,300,000
Series A Final Closing [Member]
Schedule Of Accounting Policies [Line Items]
Non-cash deemed dividends on convertible preferred stock												$ 21,800,000
Maximum [Member]
Schedule Of Accounting Policies [Line Items]
Original maturities of highly liquid investments											3 months
IPO [Member]
Schedule Of Accounting Policies [Line Items]
Common stock issued, share | shares	12,676,354
Issuance of common stock price per share | $ / shares	$ 24
Underwriters option [Member]
Schedule Of Accounting Policies [Line Items]
Common stock issued, share | shares	1,653,437
Stock Price Increased to 10% [Member]
Schedule Of Accounting Policies [Line Items]
Stock price increase/decrease percentage					10.00%
Stock price per share | $ / shares		43.97			$ 43.97						$ 43.97		43.97
Stock price increase/decrease per share | $ / shares					$ 48.37
Change in success payment expense/gain					$ 7,700,000
Stock Price Decreased to 10% [Member]
Schedule Of Accounting Policies [Line Items]
Stock price increase/decrease percentage					10.00%
Stock price per share | $ / shares		43.97			$ 43.97						43.97		43.97
Stock price increase/decrease per share | $ / shares					$ 39.57
Change in success payment expense/gain					$ 7,600,000
Stock Price Increased to 35% [Member]
Schedule Of Accounting Policies [Line Items]
Stock price increase/decrease percentage					35.00%
Stock price per share | $ / shares		43.97			$ 43.97						43.97		43.97
Stock price increase/decrease per share | $ / shares					$ 59.36
Resulting success payment gain					$ 27,300,000
Stock Price Decreased to 35% [Member]
Schedule Of Accounting Policies [Line Items]
Stock price increase/decrease percentage					35.00%
Stock price per share | $ / shares		$ 43.97			$ 43.97						$ 43.97		$ 43.97
Stock price increase/decrease per share | $ / shares					$ 28.58
Change in success payment expense/gain					$ 25,700,000

Significant Accounting Polici42

Significant Accounting Policies - Schedule of Estimated Useful Lives of Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2015
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives	5 years
Computer equipment, software and other [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives	3 years
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives	Shorter of asset's useful life or remaining term of lease

Significant Accounting Polici43

Significant Accounting Policies - Reconciliation of Net Loss to Net Loss Attributable to Common Stockholders (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								5 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net loss	$ (85,213)	$ (23,240)	$ (65,958)	$ (64,965)	$ (191,871)	$ (19,818)	$ (22,769)	$ (8,949)	$ (51,820)	$ (239,376)	$ (243,407)
Deemed dividend upon issuance of convertible preferred stock, non-cash						(52,107)	(15,357)				(67,464)
Net loss attributable to common stockholders					$ (191,871)	$ (71,925)	$ (38,126)	$ (8,949)	$ (51,820)	$ (239,376)	$ (310,871)
Weighted average number of common shares used in net loss per share attributable to common stockholders - basic and diluted									3,658,687	88,145,424	8,442,947
Net loss per share attributable to common stockholders - basic and diluted	$ (0.89)	$ (0.26)	$ (0.79)	$ (0.79)	$ (13.68)	$ (10.50)	$ (5.80)	$ (1.41)	$ (14.16)	$ (2.72)	$ (36.82)

Significant Accounting Polici44

Significant Accounting Policies - Schedule of Diluted Net Loss Per Share Attributable to Common Stockholders Due to Anti-Dilutive Effect (Detail) - shares	5 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	24,969,787	10,900,066	12,700,794
Series A convertible preferred stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	16,930,664
Series A-1 convertible preferred stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	2,250,000
Unvested restricted common stock and restricted stock units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share	5,789,123	5,476,600	8,352,714
Options to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share		5,218,939	2,720,351
Estimated number of shares issued for success payments [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from the calculation of diluted net loss per share		204,527	1,627,729

Significant Accounting Polici45

Significant Accounting Policies - Schedule of Diluted Net Loss Per Share Attributable to Common Stockholders Due to Anti-Dilutive Effect (Parenthetical) (Detail) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Success payment	$ 116.2	$ 195.9
Fred Hutchinson Cancer Research Center [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock closing price per share	$ 43.97	$ 52.22
Memorial Sloan Kettering Cancer Center [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock closing price per share	$ 43.97	52.22
Estimated number of shares issued for success payments [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock closing price per share		$ 52.22
Success payment		$ 85
Estimated number of shares issued for success payments [Member] | Fred Hutchinson Cancer Research Center [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Success payment		75
Estimated number of shares issued for success payments [Member] | Memorial Sloan Kettering Cancer Center [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Success payment	$ 10	$ 10

Acquisitions - Acquisition of S

Acquisitions - Acquisition of Stage - Additional Information (Detail) $ / shares in Units, € in Millions	May. 11, 2015USD ($)$ / sharesshares	May. 11, 2015EUR (€)shares	Dec. 31, 2015USD ($)	Dec. 31, 2015EUR (€)
Business Acquisition [Line Items]
Business combination, additional amounts on achievement of certain technical, clinical, regulatory, and commercial milestones				€ 135
Stage Cell Therapeutics GmbH [Member]
Business Acquisition [Line Items]
Prior to the acquisition, equity interest held	4.76%
Cash paid for acquisition	$ 58,496,000	€ 52.5
Aggregate shares issued in acquisition | shares	486,279	486,279
Common stock value | $	$ 22,165,000
Closing stock price | $ / shares	$ 45.58
Business combination, additional amounts on achievement of certain technical, clinical, regulatory, and commercial milestones				30
Fair value of contingent consideration in acquisition | $	$ 28,200,000		$ 28,300,000
Business acquisition, goodwill, expected tax deductible amount | $			$ 0
Novel Reagents [Member]
Business Acquisition [Line Items]
Business combination, additional amounts on achievement of certain technical, clinical, regulatory, and commercial milestones				40
Advanced Automation Technology [Member]
Business Acquisition [Line Items]
Business combination, additional amounts on achievement of certain technical, clinical, regulatory, and commercial milestones				€ 65

Acquisitions - Schedule of Purc

Acquisitions - Schedule of Purchase Consideration (Detail) $ in Thousands, € in Millions	Jun. 01, 2015USD ($)	May. 11, 2015USD ($)	May. 11, 2015EUR (€)
Stage Cell Therapeutics GmbH [Member]
Business Acquisition [Line Items]
Cash paid		$ 58,496	€ 52.5
Common stock issued		22,165
Fair value of contingent consideration		28,244
Total consideration		108,905
Fair value of 4.76% initial investment in Stage		3,682
Implied purchase price consideration for 100% equity		$ 112,587
X- BODY [Member]
Business Acquisition [Line Items]
Cash paid	$ 21,331
Common stock issued	19,400
Fair value of contingent consideration	8,944
Total consideration	50,845
X- BODY [Member] | Settlement of preexisting obligation [Member]
Business Acquisition [Line Items]
Settlement of preexisting obligation	1,123
X- BODY [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Common stock issued	$ 19,447

Acquisitions - Schedule of Pu48

Acquisitions - Schedule of Purchase Consideration (Parenthetical) (Detail) $ / shares in Units, € in Millions	Jun. 01, 2015USD ($)$ / sharesshares	May. 11, 2015USD ($)$ / sharesshares	May. 11, 2015EUR (€)shares	Dec. 31, 2015USD ($)
Business Acquisition [Line Items]
Estimated discount percentage rate of contingent consideration				17.00%
Stage Cell Therapeutics GmbH [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired		95.24%
Percentage of initial investment		4.76%
Equity percentage of purchase price consideration		100.00%
Cash paid for acquisition		$ 58,496,000	€ 52.5
Aggregate shares issued in acquisition | shares		486,279	486,279
Closing stock price | $ / shares		$ 45.58
Estimated discount percentage rate of contingent consideration		14.60%	14.60%
Step acquisition equity interest remeasurement gain | $				$ 200,000
X- BODY [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired	100.00%
Cash paid for acquisition | $	$ 21,331,000
Aggregate shares issued in acquisition | shares	366,434
Closing stock price | $ / shares	$ 53.07
Estimated discount percentage rate of contingent consideration	15.20%
Gain or loss recognized on the settlement pre-existing obligation | $	$ 0
Common Stock [Member] | X- BODY [Member]
Business Acquisition [Line Items]
Aggregate shares issued in acquisition | shares	366,434
Closing stock price | $ / shares	$ 53.07

Acquisitions - Components of Pu

Acquisitions - Components of Purchase Price Allocation (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Jun. 01, 2015	May. 11, 2015
Business Acquisition [Line Items]
Goodwill	$ 122,092
Stage Cell Therapeutics GmbH [Member]
Business Acquisition [Line Items]
Net working capital			$ 1,863
Property and equipment			651
Net assets acquired			2,514
Deferred tax liabilities			(10,801)
Acquired in-process research and development			34,457
Goodwill			86,417
Total consideration transferred			$ 112,587
X- BODY [Member]
Business Acquisition [Line Items]
Net liabilities assumed		$ (181)
Deferred tax liabilities		(1,099)
Acquired in-process research and development		16,450
Goodwill		35,675
Total consideration transferred		$ 50,845

Acquisitions - Acquisition of X

Acquisitions - Acquisition of X-Body - Additional Information (Detail) $ / shares in Units, € in Millions	Jun. 01, 2015USD ($)$ / sharesshares	Dec. 31, 2015USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2015EUR (€)
Business Acquisition [Line Items]
Business acquisition milestone payment in cash | €				€ 135
Impairment of goodwill		$ 0	$ 0
Impairment of intangible assets		0
X- BODY [Member]
Business Acquisition [Line Items]
Percentage of equity interest acquired	100.00%
Cash paid for acquisition	$ 21,331,000
Aggregate shares issued in acquisition | shares	366,434
Common stock value	$ 19,400,000
Closing stock price | $ / shares	$ 53.07
Shares of restricted common stock issued in acquisition | shares	72,831
Fair value of contingent consideration in acquisition	$ 8,900,000	9,000,000	9,000,000
Business acquisition, goodwill, expected tax deductible amount		0	0
X- BODY [Member] | Regulatory Milestone [Member]
Business Acquisition [Line Items]
Business acquisition milestone payment in cash	5,000,000
X- BODY [Member] | Type X Product [Member]
Business Acquisition [Line Items]
Business acquisition milestone payment in cash	20,000,000
X- BODY [Member] | Type X Product [Member] | Maximum [Member]
Business Acquisition [Line Items]
Business acquisition milestone payment in cash	30,000,000
X- BODY [Member] | Subsequent Type X Products [Member]
Business Acquisition [Line Items]
Business acquisition milestone payment in cash	5,000,000
X- BODY [Member] | Type Y Product [Member]
Business Acquisition [Line Items]
Business acquisition milestone payment in cash	$ 50,000,000
Stage and X-Body [Member]
Business Acquisition [Line Items]
Direct transaction cost		$ 4,500,000	$ 4,500,000

Acquisitions - Summary of Chang

Acquisitions - Summary of Changes in Carrying Amount of Goodwill (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Business Combinations [Abstract]
Goodwill acquired	$ 122,092
Ending Balance	$ 122,092

Acquisitions - Summary of Gross

Acquisitions - Summary of Gross Carrying Amount, Accumulated Amortization and Net Carrying Amount of Intangible Assets (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 50,177
Accumulated Amortization	0
Intangible Assets, Net	50,177
Acquired In-process Research and Development [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	50,177
Accumulated Amortization	0
Intangible Assets, Net	$ 50,177

Collaboration and License Agr53

Collaboration and License Agreements - Celgene - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Aug. 04, 2015	Jul. 31, 2015	Jun. 30, 2015	Dec. 31, 2015
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized during period				$ 18,215
Collaborative Arrangement [Member] | Co-development and Co-commercialization Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Global profits and losses from development and commercialization activities, percentage			30.00%
Collaborative Arrangement [Member] | Celgene [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Exercise options on collaboration agreement, term				The parties may exercise their options with respect to specified product candidates arising under programs within the scope of the collaboration until the tenth anniversary of the effective date of the Celgene Collaboration Agreement (the "Research Collaboration Term")
Upfront payment in connection with the acquisition of rights				The party exercising an option for these in-licensed or acquired programs is generally required to pay to the other party an upfront payment equal to one half of the costs incurred by other party in connection with the acquisition of rights to such programs.
Upfront cash payment		$ 150,200
Royalty payment description				The Company will also receive royalties from Celgene, for product candidates arising from the CD19 and CD22 programs, at a percentage in the mid-teens of net sales of such product candidates in the Celgene Territory, and for product candidates arising from other Company programs that are subject to a license agreement, tiered royalties on net sales of such product candidates in the Celgene Territory, at percentages ranging from the high single digits to the mid-teens, calculated based on the stage of development at which Celgene exercises its option for such program.
Collaboration agreement, term				10 years
Revenue recognized during period				$ 5,100
Fair value of common stock and embedded future stock purchase rights				$ 849,800
Collaborative Arrangement [Member] | Celgene [Member] | Co-development and Co-commercialization Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Global profits and losses from development and commercialization activities, percentage			70.00%
Collaborative Arrangement [Member] | Celgene [Member] | CD19 Program and CD20 Program [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Additional upfront fee upon exercise of option			$ 100,000
Share Purchase Agreement [Member] | Celgene [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Common stock shares sold	9,137,672		9,137,672
Aggregate cash price of common stock sold	$ 849,800
Common stock, price per share			$ 93
Share Purchase Agreement [Member] | Celgene [Member] | First Period Top-Up Rights [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of outstanding common stock to be acquired			10.00%
Share Purchase Agreement [Member] | Celgene [Member] | Second Period Top-Up Rights [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of average market price of shares			105.00%
SAR termination date, description				The "SAR Termination Date" is the later of (a) June 29, 2025, and (b) the earlier of (x) the date that is 6 months following the date that the conditions to the exercise of the Second Acquisition Right (as defined herein) are satisfied and (y) December 29, 2025.
Share Purchase Agreement [Member] | Celgene [Member] | Final Top-Up Rights [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of average market price of shares			105.00%
Reduction percentage of common stock outstanding			2.50%
Share Purchase Agreement [Member] | Celgene [Member] | Second Acquisition Right [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of outstanding common stock to be acquired			30.00%
Share Purchase Agreement [Member] | Celgene [Member] | Maximum [Member] | First Acquisition Right [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of outstanding common stock to be acquired			19.99%
Share Purchase Agreement [Member] | Celgene [Member] | Minimum [Member] | Second Acquisition Right [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of outstanding shares of common stock required to be held			17.00%

Collaboration and License Agr54

Collaboration and License Agreements - Fred Hutchinson Cancer Research Center - Additional Information (Detail)	1 Months Ended		3 Months Ended				5 Months Ended	12 Months Ended
	Dec. 31, 2015USD ($)Multiple$ / sharesshares	Oct. 31, 2013	Dec. 31, 2015USD ($)Multiple$ / shares	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2015USD ($)Multiple$ / sharesshares	Dec. 31, 2014USD ($)$ / shares
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses							$ 46,245,000	$ 205,160,000	$ 204,511,000
Estimated fair value of total success payment obligation	$ 116,200,000		$ 116,200,000					116,200,000	195,900,000
Success payment liabilities	$ 64,829,000		64,829,000					64,829,000	84,920,000
Success payment expense			$ 34,273,000	$ (25,586,000)	$ 3,961,000	$ 38,911,000		$ 51,600,000	$ 84,900,000
Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Success payments paid, shares | shares								1,601,085
Fred Hutchinson Cancer Research Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Per share common stock price required for payment | $ / shares	$ 43.97		$ 43.97					$ 43.97	$ 52.22
Success payments paid	$ 75,000,000		$ 75,000,000					$ 75,000,000
Indirect cost related to collaboration agreements	$ 3,300,000
Success payments paid, shares | shares	1,601,085
Minimum annual royalty payment after year five	$ 100,000		$ 100,000					$ 100,000
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Success payments paid, shares | shares	1,601,085
Fred Hutchinson Cancer Research Center [Member] | Range One [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	5		5					5
Per share common stock price required for payment | $ / shares	$ 20		$ 20					$ 20
Fred Hutchinson Cancer Research Center [Member] | Range Nine [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	40		40					40
Per share common stock price required for payment | $ / shares	$ 160		$ 160					$ 160
Fred Hutchinson Cancer Research Center [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments upon achievement of specified clinical and regulatory milestones								$ 6,800,000
Fred Hutchinson Cancer Research Center [Member] | Range Two [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	7.5		7.5					7.5
Per share common stock price required for payment | $ / shares	$ 30		$ 30					$ 30
Fred Hutchinson Cancer Research Center [Member] | Range Three [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	10		10					10
Per share common stock price required for payment | $ / shares	$ 40		$ 40					$ 40
Fred Hutchinson Cancer Research Center [Member] | Range Four [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	15		15					15
Per share common stock price required for payment | $ / shares	$ 60		$ 60					$ 60
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range One [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	5		5					5
Per share common stock price required for payment | $ / shares	$ 20		$ 20					$ 20
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range Nine [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	40		40					40
Per share common stock price required for payment | $ / shares	$ 160		$ 160					$ 160
Collaborative Arrangement [Member] | Fred Hutchinson Cancer Research Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreement, term		6 years
Research and development expenses							$ 3,400,000	$ 10,300,000	$ 6,900,000
Estimated fair value of total success payment obligation	$ 67,300,000		$ 67,300,000					67,300,000	139,100,000
Success payment liabilities	$ 33,800,000		$ 33,800,000					33,800,000	61,200,000
Success payment expense								44,300,000	$ 61,200,000
Collaborative Arrangement [Member] | Fred Hutchinson Cancer Research Center [Member] | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Term of success payments		8 years
Collaborative Arrangement [Member] | Fred Hutchinson Cancer Research Center [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate success payments								$ 375,000,000
Term of success payments		11 years
Collaborative Arrangement [Member] | Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of common stock price per share | $ / shares	$ 4		$ 4					$ 4

Collaboration and License Agr55

Collaboration and License Agreements - Summary of All Possible Success Payments, Payable in Cash or Publicly-Traded Equity (Detail) $ / shares in Units, $ in Millions	Dec. 31, 2015USD ($)Multiple$ / shares	Dec. 31, 2014$ / shares
Memorial Sloan Kettering Cancer Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Per share common stock price required for payment	$ 43.97	$ 52.22
Memorial Sloan Kettering Cancer Center [Member] | Common Stock [Member] | Range One [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	10
Per share common stock price required for payment	$ 40
Success payments | $	$ 10
Memorial Sloan Kettering Cancer Center [Member] | Common Stock [Member] | Range Two [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	15
Per share common stock price required for payment	$ 60
Success payments | $	$ 70
Memorial Sloan Kettering Cancer Center [Member] | Common Stock [Member] | Range Three [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	30
Per share common stock price required for payment	$ 120
Success payments | $	$ 70
Fred Hutchinson Cancer Research Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Per share common stock price required for payment	$ 43.97	$ 52.22
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range One [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	5
Per share common stock price required for payment	$ 20
Success payments | $	$ 10
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range Two [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	7.5
Per share common stock price required for payment	$ 30
Success payments | $	$ 25
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range Three [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	10
Per share common stock price required for payment	$ 40
Success payments | $	$ 40
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range Four [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	15
Per share common stock price required for payment	$ 60
Success payments | $	$ 50
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range Five [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	20
Per share common stock price required for payment	$ 80
Success payments | $	$ 50
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range Six [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	25
Per share common stock price required for payment	$ 100
Success payments | $	$ 50
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range Seven [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	30
Per share common stock price required for payment	$ 120
Success payments | $	$ 50
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range Eight [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	35
Per share common stock price required for payment	$ 140
Success payments | $	$ 50
Fred Hutchinson Cancer Research Center [Member] | Common Stock [Member] | Range Nine [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple	40
Per share common stock price required for payment	$ 160
Success payments | $	$ 50

Collaboration and License Agr56

Collaboration and License Agreements - Assumptions Used to Calculate Estimated Fair Value of Success Payment Liability (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fred Hutchinson Cancer Research Center [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value of common stock	$ 43.97	$ 52.22
Expected volatility	70.00%	75.00%
Fred Hutchinson Cancer Research Center [Member] | Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Risk free interest rate	1.89%	1.94%
Expected term (years)	5 years 9 months 15 days	6 years 9 months 15 days
Fred Hutchinson Cancer Research Center [Member] | Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Risk free interest rate	2.20%	2.16%
Expected term (years)	8 years 9 months 15 days	9 years 9 months 15 days
Memorial Sloan Kettering Cancer Center [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Fair value of common stock	$ 43.97	$ 52.22
Expected volatility	70.00%	75.00%
Memorial Sloan Kettering Cancer Center [Member] | Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Risk free interest rate	1.91%	1.95%
Expected term (years)	5 years 10 months 21 days	6 years 10 months 21 days
Memorial Sloan Kettering Cancer Center [Member] | Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Risk free interest rate	2.20%	2.16%
Expected term (years)	8 years 10 months 21 days	9 years 10 months 21 days

Collaboration and License Agr57

Collaboration and License Agreements - Memorial Sloan Kettering Cancer Center - Additional Information (Detail)	1 Months Ended	3 Months Ended				5 Months Ended	12 Months Ended
	Nov. 30, 2013	Dec. 31, 2015USD ($)Multiple$ / shares	Sep. 30, 2015USD ($)	Jun. 30, 2015USD ($)	Mar. 31, 2015USD ($)	Dec. 31, 2013USD ($)	Dec. 31, 2015USD ($)Multiple$ / shares	Dec. 31, 2014USD ($)$ / shares	Dec. 31, 2013
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses						$ 46,245,000	$ 205,160,000	$ 204,511,000
Estimated fair value of total success payment obligation		$ 116,200,000					116,200,000	195,900,000
Success payment liabilities		64,829,000					64,829,000	84,920,000
Success payment expense		$ 34,273,000	$ (25,586,000)	$ 3,961,000	$ 38,911,000		$ 51,600,000	$ 84,900,000
Memorial Sloan Kettering Cancer Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Stock price per share | $ / shares		$ 43.97					$ 43.97	$ 52.22
Memorial Sloan Kettering Cancer Center [Member] | Range One [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Estimated fair value of total success payment obligation		$ 10,000,000					$ 10,000,000
Memorial Sloan Kettering Cancer Center [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments upon achievement of specified clinical and regulatory milestones							$ 6,800,000
Common Stock [Member] | Memorial Sloan Kettering Cancer Center [Member] | Range One [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple		10					10
Stock price per share | $ / shares		$ 40					$ 40
Common Stock [Member] | Memorial Sloan Kettering Cancer Center [Member] | Range Three [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple		30					30
Stock price per share | $ / shares		$ 120					$ 120
Common Stock [Member] | Memorial Sloan Kettering Cancer Center [Member] | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple		15					15
Collaborative Arrangement [Member] | Memorial Sloan Kettering Cancer Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses						500,000	$ 4,700,000	$ 2,500,000
Estimated fair value of total success payment obligation		$ 48,900,000					48,900,000	56,800,000
Success payment liabilities		$ 31,000,000					31,000,000	23,700,000
Success payment expense							7,300,000	$ 23,700,000
Collaboration agreement, term	5 years
Collaborative Arrangement [Member] | Memorial Sloan Kettering Cancer Center [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate success payments							$ 150,000,000
Term of success payments									11 years
Collaborative Arrangement [Member] | Memorial Sloan Kettering Cancer Center [Member] | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Term of success payments									8 years
Collaborative Arrangement [Member] | Common Stock [Member] | Memorial Sloan Kettering Cancer Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Issuance of common stock price per share | $ / shares		$ 4					$ 4
Collaborative Arrangement [Member] | Common Stock [Member] | Memorial Sloan Kettering Cancer Center [Member] | Range One [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple		10					10
Stock price per share | $ / shares		$ 40					$ 40
Collaborative Arrangement [Member] | Common Stock [Member] | Memorial Sloan Kettering Cancer Center [Member] | Range Three [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Multiple of Initial Equity Value at issuance | Multiple		30					30
Stock price per share | $ / shares		$ 120					$ 120
License Agreement [Member] | Memorial Sloan Kettering Cancer Center [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront license fee paid						$ 6,900,000
Minimum annual royalty payment after year five		$ 100,000					$ 100,000

Collaboration and License Agr58

Collaboration and License Agreements - St. Jude Children's Research Hospital/ Novartis - Additional Information (Detail) - USD ($)	1 Months Ended	5 Months Ended	12 Months Ended
	Apr. 30, 2015	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
License Agreement [Member] | St. Jude Children's Research Hospital [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Minimum annual royalty payment in year one			$ 100,000
Minimum annual royalty payment in year two			100,000
Minimum annual royalty payment after year two			500,000
Reimbursement of litigation expenses		$ 200,000	5,500,000	$ 3,600,000
License Agreement [Member] | St. Jude Children's Research Hospital [Member] | Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License fee recorded as research and development expense		$ 25,000,000
License Agreement [Member] | St. Jude Children's Research Hospital [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments upon achievement of specified clinical and regulatory milestones			62,500,000
License Agreement [Member] | Penn Novartis Sublicense Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Initial license fee			12,300,000
Percentage of milestone payment reduced	50.00%
Reimbursement of milestone payment	50.00%
Settlement Agreement [Member] | St. Jude Children's Research Hospital [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Reimbursement of litigation expenses			$ 5,300,000

Collaboration and License Agr59

Collaboration and License Agreements - Seattle Children's Research Institute - Additional Information (Detail) - USD ($)	Apr. 01, 2015	Feb. 28, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expenses			$ 46,245,000	$ 205,160,000	$ 204,511,000
Collaborative Arrangement [Member] | Seattle Children's Research Institute [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaboration agreement, term		5 years		5 years
Sponsored research agreement amended expiration date				Apr. 1, 2020
Additional research funding obligations	$ 300,000
Research and development expenses				$ 2,500,000	400,000
Collaborative Arrangement [Member] | Seattle Children's Research Institute [Member] | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Clinical trial funding commitment amount				$ 3,800,000
Collaborative Arrangement [Member] | Research and Development Arrangement [Member] | Seattle Children's Research Institute [Member] | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate research funding, committed		$ 2,100,000
License Agreement [Member] | Seattle Children's Research Institute [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront license fee paid					$ 200,000
Minimum annual license maintenance payment in year one		50,000
Minimum annual license maintenance payment in year two		50,000
Minimum annual license maintenance payment in year three		50,000
Minimum annual license maintenance payment in year four		50,000
Minimum annual license maintenance payment in year five		50,000
Minimum annual license maintenance payment after year five		$ 200,000

Collaboration and License Agr60

Collaboration and License Agreements - Opus Bio - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	5 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Jan. 31, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment through issuance of common stock			$ 10,235,000		$ 64,086,000
Opus Bio [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront cash payment		$ 20,000,000
Upfront payment through issuance of common stock		64,100,000			$ 64,100,000
Issuance of common stock to strategic partner, non-cash, shares					1,602,564
Opus Bio [Member] | Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront cash payment					$ 20,000,000
License Agreement [Member] | Opus Bio [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments payable in shares of common stock	$ 52,500,000	$ 52,500,000			$ 52,500,000
Share price used in milestone payments payable in shares of common stock calculation	$ 10.92	$ 10.92			$ 10.92
Maximum shares for milestone payments payable in shares of common stock	4,807,692	4,807,692			4,807,692
Trading period used in milestone payments payable in shares of common stock calculation	30 days
License Agreement [Member] | Opus Bio [Member] | Subsequent Event [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Achievement of milestone payment, shares						408,068
License Agreement [Member] | Opus Bio [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments upon achievement of specified clinical and regulatory milestones				$ 215,000,000
Pass-through payments owed by counter party				$ 2,800,000
License Agreement [Member] | Opus Bio [Member] | Minimum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development and commercialization expenses	$ 2,500,000

Collaboration and License Agr61

Collaboration and License Agreements - Fate Therapeutics - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	5 Months Ended	12 Months Ended
	May. 31, 2015	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense		$ 46,245	$ 205,160	$ 204,511
Collaboration and License Agreement [Member] | Fate Therapeutics [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Common stock share purchased	1,000,000
Purchase price of common stock	$ 8
Ownership interest	5.00%
Research and development expense			$ 1,300
Research funding amount per year	$ 2,000
Collaboration and license agreement description			The Company also agreed to provide Fate Therapeutics with research funding of $2.0 million per year during the initial four year research term. The Company has an option to extend the collaboration for two additional years, subject to payment of an extension fee and additional annual research funding.
Research funding additional term	2 years
Research funding term	4 years
Collaboration and License Agreement [Member] | Fate Therapeutics [Member] | Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront fee	$ 5,000		$ 5,000
Collaboration and License Agreement [Member] | Fate Therapeutics [Member] | Additional Paid-in Capital [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense			$ 800

Collaboration and License Agr62

Collaboration and License Agreements - Editas Medicine - Additional Information (Detail) - USD ($)	1 Months Ended	5 Months Ended	12 Months Ended
	May. 31, 2015	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research and development expense		$ 46,245,000	$ 205,160,000	$ 204,511,000
Collaboration and License Agreement [Member] | Editas Medicine ("Editas") [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Research funding term			5 years
Research funding additional term			2 years
Research and development expense			$ 1,900,000
Collaboration and License Agreement [Member] | Editas Medicine ("Editas") [Member] | Maximum [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate research funding, committed	$ 22,000,000
Collaboration and License Agreement [Member] | Editas Medicine ("Editas") [Member] | Research and Development Expense [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront fee	$ 25,000,000

Cash Equivalents and Marketab63

Cash Equivalents and Marketable Securities - Summary of Estimated Fair Value of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Cash equivalents	$ 229,556	$ 246,323
Gross Unrealized Holding Gains, Cash equivalents	0	0
Gross Unrealized Holding Losses, Cash equivalents	0	0
Estimated Fair Value, Cash equivalents	229,556	246,323
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Cash equivalents	5,040	1,702
Gross Unrealized Holding Gains, Cash equivalents	0	0
Gross Unrealized Holding Losses, Cash equivalents	0	0
Estimated Fair Value, Cash equivalents	5,040	1,702
Marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Marketable securities	691,740	79,730
Gross Unrealized Holding Gains, Marketable securities	3
Gross Unrealized Holding Losses, Marketable securities	(730)	(58)
Estimated Fair Value, Marketable securities	691,013	79,672
Marketable securities [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Marketable securities	148,143	29,863
Gross Unrealized Holding Gains, Marketable securities	1
Gross Unrealized Holding Losses, Marketable securities	(245)	(37)
Estimated Fair Value, Marketable securities	147,899	29,826
Long-term marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Marketable securities	277,639	38,442
Gross Unrealized Holding Gains, Marketable securities	34	1
Gross Unrealized Holding Losses, Marketable securities	(4,785)	(32)
Estimated Fair Value, Marketable securities	272,888	38,411
Long-term marketable securities [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Marketable securities	65,898	3,544
Gross Unrealized Holding Gains, Marketable securities	33	1
Gross Unrealized Holding Losses, Marketable securities	(195)	(7)
Estimated Fair Value, Marketable securities	65,736	3,538
Long-term marketable securities [Member] | Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Marketable securities	7,190
Gross Unrealized Holding Losses, Marketable securities	(3,820)
Estimated Fair Value, Marketable securities	3,370
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Cash equivalents	177,164	223,745
Gross Unrealized Holding Gains, Cash equivalents	0	0
Gross Unrealized Holding Losses, Cash equivalents	0	0
Estimated Fair Value, Cash equivalents	177,164	223,745
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Cash equivalents	45,352	13,294
Gross Unrealized Holding Gains, Cash equivalents	0	0
Gross Unrealized Holding Losses, Cash equivalents	0	0
Estimated Fair Value, Cash equivalents	45,352	13,294
Commercial paper [Member] | Marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Marketable securities	73,078	1,999
Estimated Fair Value, Marketable securities	73,078	1,999
U.S. government and agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Cash equivalents	2,000	7,582
Gross Unrealized Holding Gains, Cash equivalents	0	0
Gross Unrealized Holding Losses, Cash equivalents	0	0
Estimated Fair Value, Cash equivalents	2,000	7,582
U.S. government and agency securities [Member] | Marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Marketable securities	470,519	47,868
Gross Unrealized Holding Gains, Marketable securities	2
Gross Unrealized Holding Losses, Marketable securities	(485)	(21)
Estimated Fair Value, Marketable securities	470,036	47,847
U.S. government and agency securities [Member] | Long-term marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Marketable securities	204,551	34,898
Gross Unrealized Holding Gains, Marketable securities	1
Gross Unrealized Holding Losses, Marketable securities	(770)	(25)
Estimated Fair Value, Marketable securities	$ 203,782	$ 34,873

Cash Equivalents and Marketab64

Cash Equivalents and Marketable Securities - Summary of Gross Unrealized Holding Losses and Fair Value for Investments in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	$ 602,140	$ 69,943
Marketable securities, Unrealized Losses, Less than 12 Months	(730)	(58)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	602,140	69,943
Marketable securities, Unrealized Losses, Total	(730)	(58)
Marketable securities [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	144,499	26,611
Marketable securities, Unrealized Losses, Less than 12 Months	(245)	(37)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	144,499	26,611
Marketable securities, Unrealized Losses, Total	(245)	(37)
Marketable securities [Member] | U.S. government and agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	457,641	43,332
Marketable securities, Unrealized Losses, Less than 12 Months	(485)	(21)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	457,641	43,332
Marketable securities, Unrealized Losses, Total	(485)	(21)
Long-term marketable securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	244,728	35,876
Marketable securities, Unrealized Losses, Less than 12 Months	(4,785)	(32)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	244,728	35,876
Marketable securities, Unrealized Losses, Total	(4,785)	(32)
Long-term marketable securities [Member] | Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	50,591	2,003
Marketable securities, Unrealized Losses, Less than 12 Months	(195)	(7)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	50,591	2,003
Marketable securities, Unrealized Losses, Total	(195)	(7)
Long-term marketable securities [Member] | Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	3,370
Marketable securities, Unrealized Losses, Less than 12 Months	(3,820)
Marketable securities, Fair Value, 12 Months or Greater	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0
Marketable securities, Fair Value, Total	3,370
Marketable securities, Unrealized Losses, Total	(3,820)
Long-term marketable securities [Member] | U.S. government and agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable securities, Fair Value, Less than 12 Months	190,767	33,873
Marketable securities, Unrealized Losses, Less than 12 Months	(770)	(25)
Marketable securities, Fair Value, 12 Months or Greater	0	0
Marketable securities, Unrealized Losses, 12 Months or Greater	0	0
Marketable securities, Fair Value, Total	190,767	33,873
Marketable securities, Unrealized Losses, Total	$ (770)	$ (25)

Fair Value Measurements - Sched

Fair Value Measurements - Schedule of Fair Value of Financial Assets and Liabilities Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financial Assets:
Total financial assets	$ 1,193,457	$ 364,406
Financial Liabilities:
Total financial liabilities	102,095	84,920
Money market funds [Member]
Financial Assets:
Total financial assets	177,164	223,745
Commercial paper [Member]
Financial Assets:
Total financial assets	118,430	15,293
U.S. government and agency securities [Member]
Financial Assets:
Total financial assets	675,818	90,302
Corporate debt securities [Member]
Financial Assets:
Total financial assets	218,675	35,066
Equity securities [Member]
Financial Assets:
Total financial assets	3,370
Success payment liabilities [Member]
Financial Liabilities:
Total financial liabilities	64,829	84,920
Contingent consideration [Member]
Financial Liabilities:
Total financial liabilities	37,266
Level 1 [Member]
Financial Assets:
Total financial assets	180,534	223,745
Level 1 [Member] | Money market funds [Member]
Financial Assets:
Total financial assets	177,164	223,745
Level 1 [Member] | Equity securities [Member]
Financial Assets:
Total financial assets	3,370
Level 2 [Member]
Financial Assets:
Total financial assets	1,012,923	140,661
Level 2 [Member] | Commercial paper [Member]
Financial Assets:
Total financial assets	118,430	15,293
Level 2 [Member] | U.S. government and agency securities [Member]
Financial Assets:
Total financial assets	675,818	90,302
Level 2 [Member] | Corporate debt securities [Member]
Financial Assets:
Total financial assets	218,675	35,066
Level 3 [Member]
Financial Liabilities:
Total financial liabilities	102,095	84,920
Level 3 [Member] | Success payment liabilities [Member]
Financial Liabilities:
Total financial liabilities	64,829	$ 84,920
Level 3 [Member] | Contingent consideration [Member]
Financial Liabilities:
Total financial liabilities	$ 37,266

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Fair Value of Level 3 Financial Liabilities (Detail) - Level 3 [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 84,920
Additions	37,188
Payments	(71,648)
Changes in fair value	51,635	$ 84,920
Ending balance	102,095	84,920
Success payment liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	84,920
Payments	(71,648)
Changes in fair value	51,557	84,920
Ending balance	64,829	$ 84,920
Contingent consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Additions	37,188
Changes in fair value	78
Ending balance	$ 37,266

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 01, 2015	May. 11, 2015	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of success payment obligations			$ 116,200	$ 195,900
Success payment liabilities			$ 64,829	$ 84,920
Estimated discount percentage rate of contingent consideration			17.00%
(Gain) expense recognized in change in fair value of the contingent consideration			$ 78
Stage Cell Therapeutics GmbH [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated discount percentage rate of contingent consideration		14.60%
Fair value of contingent consideration in acquisition		$ 28,200	28,300
X- BODY [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated discount percentage rate of contingent consideration	15.20%
Fair value of contingent consideration in acquisition	$ 8,900		9,000
X- BODY [Member] | Research and Development Expense [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
(Gain) expense recognized in change in fair value of the contingent consideration			$ 100
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement of contingent consideration fair value, period in which milestones are expected to achieve			2,016
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Measurement of contingent consideration fair value, period in which milestones are expected to achieve			2,043

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 43,903	$ 4,217
Less: Accumulated depreciation	(1,817)	(199)
Property and equipment, net	42,086	4,018
Construction in progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	23,214
Build-to-suit asset [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	9,910
Laboratory equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	9,706	3,921
Computer equipment, software and other [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	773	198
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, at cost	$ 300	$ 98

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1.6	$ 0.2

Accrued Liabilities - Schedule

Accrued Liabilities - Schedule of Accrued Liabilities and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Accrued Liabilities, Current [Abstract]
Accrued clinical expenses	$ 7,174	$ 564
Accrued research and development expenses	7,132	2,724
Accrued bonus expense	7,054	3,106
Accrued employee expenses	3,281	531
Accrued milestones	2,827
Accrued legal expenses	1,987	4,309
Accrued offering costs		1,456
Other	3,921	1,887
Total accrued liabilities and other current liabilities	$ 33,376	$ 14,577

Build-to-Suit Lease Obligation

Build-to-Suit Lease Obligation - Additional Information (Detail) $ in Thousands	1 Months Ended
	Feb. 28, 2015USD ($)ft²	Dec. 31, 2015USD ($)
Build To Suit Lease Obligation [Line Items]
Build-to-suit lease obligation current liability		$ 400
Build-to-suit lease obligation non-current liability		$ 9,294
Bothell Lease [Member]
Build To Suit Lease Obligation [Line Items]
Operating lease space, in square feet | ft²	68,000
Lease commenced date	Mar. 1, 2015
Lease agreement date	2015-02
Bothell Lease [Member] | Property, Plant and Equipment [Member]
Build To Suit Lease Obligation [Line Items]
Capitalized value of build-to-suit property	$ 9,900

Common Stock - Additional Infor

Common Stock - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Common stock, shares outstanding	97,247,058	82,073,647
Common stock voting rights	One vote
Preferred stock, shares outstanding	0	0
Restricted Stock Awards [Member]
Class of Stock [Line Items]
Unvested restricted stock outstanding	5,153,445	8,352,714
Stock Options And Vesting of Outstanding Restricted Stock Units [Member]
Class of Stock [Line Items]
Common stock reserved for future issuance	5,614,926	2,720,351

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Nov. 16, 2015	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Jan. 01, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to stock options and restricted stock			$ 107.2
Fair value of awards vested		$ 0.4	158.5	$ 21.4
Intrinsic value of options exercised			$ 10.9
Options exercised			268,765	0
2013 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares unissued and available for future award			453,547
Awards vesting period under the plans			4 years
2014 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Initial share reserve under the plan				6,200,000
Number of shares transferred from other plan				453,547
Maximum annual increase in the shares available for issuance			4.00%
Number of shares available for issuance			7,021,850
Awards vesting period under the plans			4 years
2014 Stock Incentive Plan [Member] | Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increase in shares available for issuance					4,096,020
Two Thousand Fourteen Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Initial share reserve under the plan			1,500,000
Maximum annual increase in the shares available for issuance			1.50%
Number of shares available for issuance			2,788,731
Maximum employee subscription rate			15.00%
Discount rate from fair value of common stock	85.00%		85.00%
Closing price per share	$ 20.40
Number of shares issued			67,664	0
Two Thousand Fourteen Employee Stock Purchase Plan [Member] | Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual increase in shares available for issuance					1,536,008
Options to purchase common stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to stock options			$ 86.9
Unrecognized compensation cost, period			3 years 22 days
Weighted average grant date fair value of options granted			$ 32.51	$ 4.86
Restricted Stock and RSUs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost related to non-vested restricted stock			$ 20.3
Unrecognized compensation cost, period			2 years 4 months 21 days

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	5 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 125	$ 31,941	$ 6,504
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 125	17,089	2,908
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense		$ 14,852	$ 3,596

Stock-Based Compensation - Su75

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Parenthetical) (Detail) - USD ($) $ in Thousands	5 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense recognized	$ 125	$ 31,941	$ 6,504
Service Providers [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense recognized		8,100	2,800
Former Co Founding Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense recognized		$ 6,200	$ 2,500

Stock-Based Compensation - Su76

Stock-Based Compensation - Summary of Restricted Stock and RSU Activity (Detail) - Restricted Stock and RSUs [Member]	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unvested shares, Beginning balance | shares	8,352,714
Granted, Shares | shares	395,987
Vested, Shares | shares	(3,245,512)
Forfeited, Shares | shares	(26,589)
Unvested shares, Ending balance | shares	5,476,600
Unvested shares, Weighted Average Fair Value at Date of Grant per Share, Beginning balance | $ / shares	$ 1.46
Granted, Weighted Average Fair Value at Date of Grant per Share | $ / shares	49.51
Vested, Weighted Average Fair Value at Date of Grant per Share | $ / shares	0.51
Forfeited, Weighted Average Fair Value at Date of Grant per Share | $ / shares	0.60
Unvested shares, Weighted Average Fair Value at Date of Grant per Share, Ending balance | $ / shares	$ 3.72

Stock-Based Compensation - Su77

Stock-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Stock Options, Outstanding, Beginning Balance	2,720,351
Number of Stock Options, Granted	2,914,406
Number of Stock Options, Exercised	(268,765)	0
Number of Stock Options, Cancelled	(147,053)
Number of Stock Options, Outstanding, Ending Balance	5,218,939	2,720,351
Number of Stock Options, Exercisable	806,477
Weighted Average Exercise Price per Share, Outstanding, Beginning Balance	$ 7.23
Weighted Average Exercise Price per Share, Granted	49.08
Weighted Average Exercise Price per Share, Exercised	7.39
Weighted Average Exercise Price per Share, Cancelled	19.20
Weighted Average Exercise Price per Share, Outstanding, Ending Balance	30.25	$ 7.23
Weighted Average Exercise Price per Share, Exercisable	$ 16.17
Weighted Average Remaining Contractual Life (in years), Outstanding	9 years 1 month 17 days
Weighted Average Remaining Contractual Life (in years), Exercisable	8 years 8 months 12 days
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 86,609
Aggregate Intrinsic Value, Exercisable	$ 23,160

Stock-Based Compensation - Su78

Stock-Based Compensation - Summary of Material Factors Incorporated in Black-Scholes Model in Estimating Fair Value of Options Granted to Employees and Consultants (Detail)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk free interest rate, minimum	1.53%	1.59%
Risk free interest rate, maximum	2.35%	2.17%
Expected volatility		75.00%
Expected volatility	70.00%
Expected volatility	80.00%
Expected dividend yield	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life	6 years 7 days	6 years 3 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected life	10 years	10 years

Accumulated Other Comprehensi79

Accumulated Other Comprehensive Loss - Components of Accumulated Other Comprehensive Income (Loss) and Adjustments to Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ (90)
Other comprehensive income (loss)	(5,993)	$ (90)
Ending balance	(6,083)	(90)
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss)	(605)
Ending balance	(605)
Net Unrealized Gains (Losses) on Available-For-Sale Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(90)
Other comprehensive income (loss)	(5,388)	(90)
Ending balance	(5,478)	(90)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	(90)
Other comprehensive income (loss)	(5,993)	(90)
Ending balance	$ (6,083)	$ (90)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	Aug. 04, 2015	Jul. 31, 2015	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Line Items]
Benefit for income taxes				$ 1,700	$ 2,760
Pre-tax loss			$ 51,820		$ 242,136	$ 243,407
Net Operating Loss and tax credit carryforwards, beginning expiration year					2,033
NOL carryforwards benefit recorded to equity when utilized					$ 3,500
Cumulative changes in the ownership interest of significant stockholders					50.00%
Increases in valuation allowance					$ 89,200	78,800
United States [Member]
Income Tax Disclosure [Line Items]
Pre-tax loss			$ 51,820		236,028	243,407
Federal net operating loss carryforward				167,300	167,300	51,100
Foreign [Member]
Income Tax Disclosure [Line Items]
Pre-tax loss					6,108
Federal tax credits				14,600	14,600	$ 1,800
GERMANY
Income Tax Disclosure [Line Items]
Federal net operating loss carryforward				$ 4,900	4,900
Share Purchase Agreement [Member] | Celgene [Member]
Income Tax Disclosure [Line Items]
Aggregate cash price of common stock sold	$ 849,800
Collaborative Arrangement [Member] | Celgene [Member]
Income Tax Disclosure [Line Items]
Upfront cash payment		$ 150,200
X- BODY [Member]
Income Tax Disclosure [Line Items]
Benefit for income taxes					$ 1,100

Income Taxes - Schedule of Loss

Income Taxes - Schedule of Loss Before Income Taxes Attributable to Tax Jurisdictions (Detail) - USD ($) $ in Thousands	5 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Line Items]
Loss before income taxes	$ 51,820	$ 242,136	$ 243,407
United States [Member]
Income Tax Disclosure [Line Items]
Loss before income taxes	$ 51,820	236,028	$ 243,407
Foreign [Member]
Income Tax Disclosure [Line Items]
Loss before income taxes		$ 6,108

Income Taxes - Components of th

Income Taxes - Components of the Benefit for Income Taxes (Detail) - USD ($) $ in Thousands	8 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2015
Deferred:
United States		$ 1,100
Foreign		1,660
Total deferred		2,760
Provision for income taxes	$ 1,700	$ 2,760

Income Taxes - Summary of Incom

Income Taxes - Summary of Income Tax Rate Reconciliation (Detail)	5 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal statutory tax	34.00%	35.00%	34.00%
Foreign tax rate differential		(0.10%)
Valuation allowance	(30.00%)	(36.20%)	(32.40%)
Tax credits	0.20%	3.80%	0.70%
Other	(4.20%)	(1.40%)	(2.30%)
Total	0.00%	1.10%	0.00%

Income Taxes - Components of Ne

Income Taxes - Components of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 56,862	$ 17,391
Tax credit carryforwards	14,561	1,799
Acquired technology	57,369	45,534
Success payments	47,745	28,872
Stock compensation	4,342	115
Other	5,019	1,430
Gross deferred tax assets	185,898	95,141
Valuation allowance	(183,597)	(94,368)
Deferred tax assets, net of valuation allowance	2,301	773
Deferred tax liabilities:
Acquired technology	(10,540)
Other	(707)	(773)
Deferred tax liabilities	(11,247)	$ (773)
Net deferred tax liabilities	$ (8,946)

Commitments and Contingencies -

Commitments and Contingencies - Summary of Company's Future Minimum Lease Commitments (Detail) $ in Thousands	Dec. 31, 2015USD ($)
Commitments and Contingencies Disclosure [Abstract]
2,016	$ 3,890
2,017	4,983
2,018	10,652
2,019	10,901
2,020	11,156
Thereafter	42,031
Total minimum lease payments	$ 83,613

Commitments and Contingencies86

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	5 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Commitments [Line Items]
Rent expense		$ 2.3	$ 0.9	$ 0.1
St. Jude Children's Research Hospital [Member]
Other Commitments [Line Items]
Litigation expense reimbursement	$ 0.2	$ 5.5	$ 3.6

Related-Party Transactions - Ad

Related-Party Transactions - Additional Information (Detail)	Dec. 31, 2015
Celgene [Member] | Minimum [Member]
Related Party Transaction [Line Items]
Common stock holding percentage	5.00%

Selected Quarterly Financial 88

Selected Quarterly Financial Data - Schedule of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								5 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Loss from operations	$ (87,442)	$ (23,533)	$ (67,965)	$ (65,160)	$ (191,940)	$ (19,818)	$ (12,680)	$ (8,320)	$ (51,678)	$ (244,100)	$ (232,758)
Net loss	$ (85,213)	$ (23,240)	$ (65,958)	$ (64,965)	(191,871)	(19,818)	(22,769)	(8,949)	(51,820)	(239,376)	(243,407)
Deemed dividend upon issuance of convertible preferred stock, non-cash						(52,107)	(15,357)				(67,464)
Net loss attributable to common stockholders					$ (191,871)	$ (71,925)	$ (38,126)	$ (8,949)	$ (51,820)	$ (239,376)	$ (310,871)
Net loss per share attributable to common stockholders, basic and diluted	$ (0.89)	$ (0.26)	$ (0.79)	$ (0.79)	$ (13.68)	$ (10.50)	$ (5.80)	$ (1.41)	$ (14.16)	$ (2.72)	$ (36.82)

Selected Quarterly Financial 89

Selected Quarterly Financial Data - Schedule of Quarterly Financial Information (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended					5 Months Ended	12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Quarterly Financial Information [Line Items]
Success payment expense	$ 34,273	$ (25,586)	$ 3,961	$ 38,911			$ 51,600	$ 84,900
Upfront payment through issuance of common stock						$ 10,235		64,086
Editas and Fate collaborations [Member]
Schedule Of Quarterly Financial Information [Line Items]
Upfront fees to acquire technology			$ 30,800
FHCRC and MSK [Member]
Schedule Of Quarterly Financial Information [Line Items]
Success payment expense					$ 83,400
Opus Bio [Member]
Schedule Of Quarterly Financial Information [Line Items]
Upfront fees to acquire technology					84,100
Upfront cash payment					20,000
Upfront payment through issuance of common stock					$ 64,100			$ 64,100

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event [Member] $ in Millions	1 Months Ended
	Jan. 31, 2016USD ($)shares
Opus Bio [Member]
Subsequent Event [Line Items]
Achievement of milestone payment | $	$ 20
License Agreement [Member] | Opus Bio [Member]
Subsequent Event [Line Items]
Achievement of milestone payment, shares | shares	408,068
AbVitro Inc [Member]
Subsequent Event [Line Items]
Cash paid for acquisition | $	$ 78
Aggregate shares issued in acquisition | shares	1,289,188

Uncategorized Items - juno-2015

Label	Element	Value
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	$ 125,000
Stock Issued During Period, Value, New Issues	us-gaap_StockIssuedDuringPeriodValueNewIssues	387,000
Stock Issued During Period, Value, Acquisitions	us-gaap_StockIssuedDuringPeriodValueAcquisitions	18,000
Stock Issued During Period, Value, Issued for Services	us-gaap_StockIssuedDuringPeriodValueIssuedForServices	3,926,000
Additional Paid-in Capital [Member]
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition	us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue	125,000
Stock Issued During Period, Value, New Issues	us-gaap_StockIssuedDuringPeriodValueNewIssues	387,000
Stock Issued During Period, Value, Acquisitions	us-gaap_StockIssuedDuringPeriodValueAcquisitions	18,000
Fair Value Of Convertible Preferred Stock Option At Issuance	juno_FairValueOfConvertiblePreferredStockOptionAtIssuance	3,971,000
Stock Issued During Period, Value, Issued for Services	us-gaap_StockIssuedDuringPeriodValueIssuedForServices	$ 3,925,000
Common Stock [Member]
Stock Issued During Period, Shares, Acquisitions	us-gaap_StockIssuedDuringPeriodSharesAcquisitions	225,000
Stock Issued During Period Shares Share-based Compensation Expense	juno_StockIssuedDuringPeriodSharesSharebasedCompensationExpense	918,859
Stock Issued During Period, Shares, New Issues	us-gaap_StockIssuedDuringPeriodSharesNewIssues	1,460,413
Stock Issued During Period, Shares, Issued for Services	us-gaap_StockIssuedDuringPeriodSharesIssuedForServices	3,774,998
Stock Issued During Period, Value, Issued for Services	us-gaap_StockIssuedDuringPeriodValueIssuedForServices	$ 1,000
Retained Earnings [Member]
Net Income (Loss) Attributable to Parent	us-gaap_NetIncomeLoss	(51,820,000)
Series A Preferred Stock [Member]
Issuance Of Convertible Preferred Stock	juno_IssuanceOfConvertiblePreferredStock	(289,000)
Series A Preferred Stock [Member] | Additional Paid-in Capital [Member]
Issuance Of Convertible Preferred Stock	juno_IssuanceOfConvertiblePreferredStock	$ (289,000)
Series A Preferred Stock [Member] | Convertible Preferred Stock [Member]
Stock Issued During Period, Shares, Acquisitions	us-gaap_StockIssuedDuringPeriodSharesAcquisitions	263,747
Issuance Of Convertible Preferred Stock	juno_IssuanceOfConvertiblePreferredStock	$ 66,668,000
Stock Issued During Period, Value, Acquisitions	us-gaap_StockIssuedDuringPeriodValueAcquisitions	$ 1,055,000
Issuance Of Convertible Preferred Stock Shares	juno_IssuanceOfConvertiblePreferredStockShares	16,666,917
Series A- One Preferred Stock [Member] | Convertible Preferred Stock [Member]
Stock Issued During Period, Shares, Acquisitions	us-gaap_StockIssuedDuringPeriodSharesAcquisitions	2,250,000
Stock Issued During Period, Value, Acquisitions	us-gaap_StockIssuedDuringPeriodValueAcquisitions	$ 4,860,000