bluebird bio (BLUE) 10-Q 2 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Oct. 28, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
Trading Symbol	BLUE
Entity Registrant Name	bluebird bio, Inc.
Entity Central Index Key	1,293,971
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		37,303,678

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 245,154	$ 164,269
Marketable securities	355,806	353,680
Prepaid expenses and other current assets	7,875	6,016
Total current assets	608,835	523,965
Marketable securities	126,681	347,814
Property and equipment, net	131,737	82,614
Intangible assets, net	21,634	24,456
Goodwill	13,128	13,128
Restricted cash and other non-current assets	16,247	10,360
Total assets	918,262	1,002,337
Current liabilities:
Accounts payable	6,710	6,334
Accrued expenses and other current liabilities	54,672	28,145
Deferred revenue, current portion	6,209	5,889
Total current liabilities	67,591	40,368
Deferred rent, net of current portion	10,995	8,294
Deferred revenue, net of current portion	41,756	35,959
Contingent consideration, net of current portion	3,267	5,082
Construction financing lease obligation	99,991	61,901
Other non-current liabilities	149	237
Total liabilities	223,749	151,841
Commitments and contingencies (Note 7)
Stockholders’ equity:
Preferred stock, $0.01 par value, 5,000 shares authorized; 0 shares issued and outstanding at September 30, 2016 and December 31, 2015
Common stock, $0.01 par value, 125,000 shares authorized; 37,296 and 36,894 shares issued and outstanding at September 30, 2016 and December 31, 2015, respectively	373	369
Additional paid-in capital	1,201,286	1,166,585
Accumulated other comprehensive loss	(836)	(2,291)
Accumulated deficit	(506,310)	(314,167)
Total stockholders’ equity	694,513	850,496
Total liabilities and stockholders’ equity	$ 918,262	$ 1,002,337

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2016	Dec. 31, 2015
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
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	$ 0.01	$ 0.01
Common stock, shares authorized	125,000,000	125,000,000
Common stock, shares issued	37,296,000	36,894,000
Common stock, shares outstanding	37,296,000	36,894,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenue:
Collaboration revenue	$ 1,552	$ 1,324	$ 4,603	$ 12,607
Total revenue	1,552	1,324	4,603	12,607
Operating expenses:
Research and development	63,971	30,395	147,642	98,380
General and administrative	14,623	13,704	48,941	31,765
Change in fair value of contingent consideration	1,098	352	3,515	2,540
Total operating expenses	79,692	44,451	200,098	132,685
Loss from operations	(78,140)	(43,127)	(195,495)	(120,078)
Other income, net	937	263	2,803	630
Loss before income taxes	(77,203)	(42,864)	(192,692)	(119,448)
Income tax benefit (expense)	178	(60)	549	(60)
Net loss	$ (77,025)	$ (42,924)	$ (192,143)	$ (119,508)
Net loss per share - basic and diluted:	$ (2.07)	$ (1.18)	$ (5.19)	$ (3.52)
Weighted-average number of common shares used in computing net loss per share - basic and diluted:	37,201	36,384	37,026	33,979
Other comprehensive (loss) income:
Unrealized (loss) gain on available-for-sale securities, net of tax (benefit) expense of ($0.1) and $0.8 million for the three and nine months ended September 30, 2016, respectively	$ (194)	$ 103	$ 1,455	$ 121
Comprehensive loss	$ (77,219)	$ (42,821)	$ (190,688)	$ (119,387)

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) (Parenthetical) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2016
Income Statement [Abstract]
Unrealized (loss) gain on available-for-sale securities tax (benefit) expense	$ (0.1)	$ 0.8

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating activities
Net loss	$ (192,143)	$ (119,508)
Adjustments to reconcile net loss to net cash used in operating activities:
Change in fair value of contingent consideration	2,099	2,015
Depreciation and amortization	7,132	5,381
Stock-based compensation expense	30,831	31,011
Other non-cash items	2,166	528
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(3,857)	(2,717)
Accounts payable	1,210	623
Accrued expenses and other liabilities	24,099	5,320
Deferred revenue	6,117	12,643
Deferred rent	1,805	(640)
Net cash (used in) operating activities	(120,541)	(65,344)
Investing activities
Restricted cash	(4,379)	(8,816)
Purchase of property and equipment	(15,005)	(3,618)
Purchases of marketable securities	(145,135)	(470,499)
Proceeds from maturities of marketable securities	356,684	132,239
Proceeds from sales of marketable securities	7,500
Net cash provided by (used in) investing activities	199,665	(350,694)
Financing activities
Cash paid for contingent purchase price consideration	(2,025)	(453)
Proceeds from public offering of common stock, net of issuance costs		477,247
Proceeds from issuance of common stock	3,786	8,909
Net cash provided by financing activities	1,761	485,703
Increase in cash and cash equivalents	80,885	69,665
Cash and cash equivalents at beginning of period	164,269	347,845
Cash and cash equivalents at end of period	245,154	417,510
Non-cash investing and financing activities:
Construction financing lease obligation	38,090	43,777
Purchases of property and equipment included in accounts payable and accrued expenses	2,479	1,475
Stock option exercise proceeds receivable	$ 374	$ 24

Description of the business

Description of the business	9 Months Ended
	Sep. 30, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Description of the business	1. Description of the business bluebird bio, Inc. (the “Company” or “bluebird”) was incorporated in Delaware on April 16, 1992, and is headquartered in Cambridge, Massachusetts. The Company researches, develops, manufactures and plans to commercialize gene therapies for the treatment of severe genetic and rare diseases and in the field of T cell-based immunotherapy. Since its inception, the Company has devoted substantially all of its resources to its research and development efforts relating to its product candidates, including activities to manufacture product candidates, conduct clinical studies of its product candidates, perform preclinical research to identify new product candidates and provide general and administrative support for these operations.

Summary of significant accounti

Summary of significant accounting policies and basis of presentation	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Summary of significant accounting policies and basis of presentation	2. Summary of significant accounting policies and basis of presentation Basis of presentation and principles of consolidation The accompanying condensed consolidated financial statements are unaudited and have been prepared by the Company in accordance with accounting principles generally accepted in the United States (“GAAP”) as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These interim condensed consolidated financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the interim periods ended September 30, 2016 and 2015. The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2015, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on February 25, 2016. The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries: Precision Genome Engineering, Inc. (“Pregenen”), bluebird bio France – SARL, bluebird bio Australia Pty Ltd., bluebird bio (UK) Ltd., bluebird bio (Bermuda) Ltd. Summary of accounting policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2015, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K. There have been no material changes in the Company’s significant accounting policies during the nine months ended September 30, 2016. Net income (loss) per share Basic net income (loss) per share is calculated by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding during the period. Diluted net income per share is calculated by dividing the net income attributable to common stockholders by the weighted-average number of common stock equivalent shares outstanding for the period, including any dilutive effect from outstanding stock options, unvested restricted stock, restricted stock units, employee stock purchase plan, and warrants using the treasury stock method. Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Estimates are used in the following areas, among others: fair value estimates used to assess potential impairment of long-lived assets, construction financing lease obligations, contingent consideration, stock-based compensation expense, accrued expenses, revenue and income taxes. Actual results could materially differ from those estimates. Recently issued accounting pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“Topic 606”), which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. The new standard will be effective on January 1, 2018 and earlier application is permitted only for annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. The Company is currently evaluating the potential impact that Topic 606 may have on its financial position and results of operations. In February 2016, the FASB issued ASU 2016-02, Leases , (“ASU 2016-02”) , which requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. The new standard includes a short-term lease exception for leases with a term of 12 months or less, as part of which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases using classification criteria that are substantially similar to the previous guidance. The new standard will be effective beginning January 1, 2019, and early adoption is permitted for public entities. The Company is currently evaluating the potential impact ASU 2016-02 may have on its financial position and results of operations. In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (“ASU No. 2016-09”), which simplifies share-based payment accounting through a variety of amendments. The standard will be effective for annual reporting periods and interim periods within those annual periods, beginning after December 15, 2016, and early adoption is permitted. The Company is currently evaluating the potential impact ASU 2016-09 may have on its financial position and results of operations. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments (“Topic 230”). The new standard clarifies certain aspects of the statement of cash flows, including the classification of contingent consideration payments made after a business combination and several other clarifications not currently applicable to the Company. The new standard also clarifies that an entity should determine each separately identifiable source or use within the cash receipts and cash payments on the basis of the nature of the underlying cash flows. In situations in which cash receipts and payments have aspects of more than one class of cash flows and cannot be separated by source or use, the appropriate classification should depend on the activity that is likely to be the predominant source or use of cash flows for the item. The new standard will be effective for the Company on January 1, 2018. The adoption of this standard is not expected to have a material impact on our statements of cash flows upon adoption.

Marketable Securities

Marketable Securities	9 Months Ended
	Sep. 30, 2016
Investments Debt And Equity Securities [Abstract]
Marketable securities	3. Marketable securities The following table summarizes the available-for-sale securities held at September 30, 2016 and December 31, 2015 (in thousands): Description Amortized Cost Unrealized Gains Unrealized Losses Fair Value September 30, 2016 U.S. government agency securities and treasuries $ 475,344 $ 91 $ (164 ) $ 475,271 Certificates of deposit 7,200 16 — 7,216 Total $ 482,544 $ 107 $ (164 ) $ 482,487 December 31, 2015 U.S. government agency securities and treasuries $ 689,425 $ 22 $ (2,300 ) $ 687,147 Certificates of deposit 14,360 — (13 ) 14,347 Total $ 703,785 $ 22 $ (2,313 ) $ 701,494 No available-for-sale securities held as of September 30, 2016 or December 31, 2015 had remaining maturities greater than three years.

Fair value measurements

Fair value measurements	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Fair value measurements	4. Fair value measurements The following table sets forth the Company’s assets and liabilities that are measured at fair value on a recurring basis as of September 30, 2016 and December 31, 2015 (in thousands): Description Total Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) September 30, 2016 Assets: Cash and cash equivalents $ 245,154 $ 245,154 $ — $ — Marketable securities: U.S. government agency securities and treasuries 475,271 — 475,271 — Certificates of deposit 7,216 — 7,216 — Total assets $ 727,641 $ 245,154 $ 482,487 $ — Liabilities: Contingent consideration $ 7,180 $ — $ — $ 7,180 Total liabilities $ 7,180 $ — $ — $ 7,180 December 31, 2015 Assets: Cash and cash equivalents $ 164,269 $ 158,269 $ 6,000 $ — Marketable securities: U.S. government agency securities and treasuries 687,147 — 687,147 — Certificates of deposit 14,347 — 14,347 — Total assets $ 865,763 $ 158,269 $ 707,494 $ — Liabilities: Contingent consideration $ 8,665 $ — $ — $ 8,665 Total liabilities $ 8,665 $ — $ — $ 8,665 Cash and cash equivalents The Company considers all highly liquid securities with original final maturities of three months or less from the date of purchase to be cash equivalents. As of September 30, 2016, cash and cash equivalents comprise funds in cash, money market accounts, and federally insured deposits. As of December 31, 2015, cash and cash equivalents comprise funds in cash, money market accounts, U.S. Treasury securities and federally insured deposits. Marketable securities The amortized cost of available-for-sale securities is adjusted for amortization of premiums and accretion of discounts to maturity. At September 30, 2016 and December 31, 2015, the balance in the Company’s accumulated other comprehensive loss was composed solely of activity related to the Company’s available-for-sale marketable securities. There were no material realized gains The aggregate fair value of securities held by the Company in an unrealized loss position for less than twelve months as of September 30, 2016 and December 31, 2015 was $ 255.8 Contingent consideration On June 30, 2014, the Company acquired Pregenen. In connection with the acquisition, the Company recorded contingent consideration pertaining to the amounts potentially payable to Pregenen’s former equityholders pursuant to the Stock Purchase Agreement (the “Stock Purchase Agreement”) by and among the Company, Pregenen and Pregenen’s former equityholders. 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. Future changes in the fair value of contingent consideration related to updated assumptions and estimates are recognized within the condensed consolidated statements of operations and comprehensive loss. 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, considerable judgment is required to interpret the market and internal 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 and internal 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 preclinical, clinical and commercial milestones, the period in which these milestones are expected to be achieved ranging from 2017 to 2026 and discount rates ranging from 9.9 to 12.7%. The table below provides a roll-forward of fair value of the Company’s contingent consideration obligations, which include Level 3 inputs (in thousands): Nine Months Ended September 30, 2016 Beginning balance $ 8,665 Additions — Changes in fair value 3,515 Payments (5,000 ) Ending balance $ 7,180 The Company may be required to make up to $129.0 million in remaining future contingent cash payments to the former equityholders of Pregenen upon the achievement of certain milestones related to the Pregenen technology, of which $9.0 million relates to preclinical milestones, $20.1 million relates to clinical milestones, and $99.9 million relates to commercial milestones. As of September 30, 2016, million of the fair value of the Company’s total contingent consideration obligations was reflected as a component of accrued expenses and other current liabilities within the condensed consolidated balance sheets, with the remaining balance of $3.3 million reflected as a non-current liability.

Property and equipment, net

Property and equipment, net	9 Months Ended
	Sep. 30, 2016
Property Plant And Equipment [Abstract]
Property and equipment, net	5. Property and equipment, net Property and equipment, net, consists of the following (in thousands): September 30, 2016 December 31, 2015 Computer equipment and software $ 1,350 $ 1,259 Office equipment 1,427 1,104 Laboratory equipment 15,273 10,520 Leasehold improvements 13,839 11,010 Construction-in-progress 110,922 65,542 Total property and equipment, gross 142,811 89,435 Less accumulated depreciation and amortization (11,074 ) (6,821 ) Total property and equipment, net $ 131,737 $ 82,614 Construction-in-progress as of September 30, 2016 includes $109.7

Accrued expenses and other curr

Accrued expenses and other current liabilities	9 Months Ended
	Sep. 30, 2016
Payables And Accruals [Abstract]
Accrued expenses and other current liabilities	6. Accrued expenses and other current liabilities Accrued expenses and other current liabilities consist of the following (in thousands): September 30, 2016 December 31, 2015 Employee compensation $ 8,920 $ 5,935 Accrued goods and services 23,855 15,876 Accrued license and milestone fees 15,208 277 Accrued professional fees 2,103 1,014 Deferred rent, current portion 68 964 Contingent consideration, current portion 3,913 3,584 Other 605 495 Total accrued expenses and other current liabilities $ 54,672 $ 28,145 Accrued license and milestone fees as of September 30, 2016 includes a $15.0 million upfront fee related to a research collaboration and license agreement entered into during the third quarter of 2016. This upfront fee was paid in the fourth quarter of 2016.

Commitments and contingencies

Commitments and contingencies	9 Months Ended
	Sep. 30, 2016
Commitments And Contingencies Disclosure [Abstract]
Commitments and contingencies	7. Commitments and contingencies The Company is party to various agreements, principally relating to licensed technology, that require future payments relating to milestones not met at September 30, 2016 and December 31, 2015 or royalties on future sales of specified products. The Company enters into standard indemnification agreements in the ordinary course of business. Pursuant to these agreements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified party for losses suffered or incurred by the indemnified party, generally the Company’s business partners or customers, in connection with claims by any third party with respect to the Company’s products or business activities. The term of these indemnification agreements is generally perpetual any time after execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements. The Company’s wholly-owned subsidiary bluebird bio France – SARL participates in the French Crédit d’Impôt Recherche (“CIR”) program, which allows companies to monetize up to 30% of eligible research expenses. As of September 30, 2016, the Company received aggregate reimbursement of €2.3 million related to years 2013 through 2015. The Company Operating Lease Commitments On June 3, 2013, the Company entered into a nine-year building lease for approximately 43,600 square feet of space located at 150 Second Street, Cambridge, Massachusetts, which commenced in December 2013. This lease was amended in June 2014 to add approximately 9,900 square feet. The lease originally had monthly lease payments of $0.2 million for the first 12 months, which increased to $0.3 million per month beginning in December 2014 due to the lease amendment, with annual rent escalations thereafter. Rent expense is recognized on a straight-line basis over the term of the lease. The Company has the option to extend this lease by an additional five years. The lease provided a contribution from the landlord towards the initial build-out of the space of up to $7.8 million. The Company capitalizes the leasehold improvements as property and equipment and records the landlord incentive payments received as deferred rent and amortizes these amounts as reductions to rent expense over the lease term. In addition, i $0.6 million as of September 30, 2016. On September 30, 2016, the Company entered into an Assignment and Assumption of Lease (“Assignment”) relating to its lease at 150 Second Street. Under the Assignment, the Company will assign all of its rights, interests, obligations and responsibilities under the lease, to be effective as of the later of May 1, 2017 or the first day following the Company’s surrender of the leased premises in accordance with the lease. The Company expects to vacate the premises by mid-2017 and as a result, no longer expects to pay $20.6 million in lease payments between 2017 and 2022, including $2.2 million in 2017, $3.5 million in 2018, $3.6 million in 2019, $3.7 million in 2020 and $7.6 million in 2021 and thereafter. On June 29, 2015, the Company entered into a lease agreement for additional office space located at 215 First Street, Cambridge, Massachusetts. Under the terms of the lease, the Company leased approximately 15,120 square feet starting on July 13, 2015 for $0.5 million per year in base rent, which is subject to a 3% annual rent increase plus certain operating expenses and taxes. The lease will continue until the end of the 60 th th On June 3, 2016, the Company entered into a strategic manufacturing agreement for the future commercial production of the Company’s Lenti-D and LentiGlobin product candidates with a contract manufacturing organization. Under this 12 year agreement, the contract manufacturing organization will complete the design, construction, validation and process validation of the leased suites prior to anticipated commercial launch of the product candidates. During construction, the Company is required to pay $12.5 million upon the achievement of certain construction milestones, and may pay up to $8.0 million in additional construction milestones if the Company elects its option to lease additional suites. The Company paid $2.0 million for the achievement of the first milestone during the third quarter of 2016, which is reflected as a component of other non-current assets within the condensed consolidated balance sheets. 60 Binney Street Lease Commitments On September 21, 2015, the Company entered into a lease agreement, which was amended for certain administrative matters on June 21, 2016, for additional office and laboratory space located in a building (the “Building”) under construction at 60 Binney Street, Cambridge, Massachusetts (the “60 Binney Lease”). Under the terms of the 60 Binney Lease, starting on October 1, 2016, the Company will lease approximately 253,108 square feet of office and laboratory space at $72.50 per square foot per year, or $18.4 million per year in base rent, which is subject to scheduled annual rent increases of 1.75% plus certain operating expenses and taxes. The Company also executed a $9.2 million letter of credit upon signing the 60 Binney Lease, which was required to be collateralized with a bank account at a financial institution in accordance with the 60 Binney Lease agreement. This letter of credit was increased to $13.8 million during the third quarter of 2016 as required under the terms of the lease. Subject to the terms of the lease and certain reduction requirements specified therein, including market capitalization requirements, this amount may decrease back to $9.2 million over time. The 60 Binney Lease will continue until the end of the 120 th Because the Company is involved in the construction project, including having responsibility to pay for a portion of the costs of finish work and mechanical, electrical, and plumbing elements of the Building, the Company is deemed for accounting purposes to be the owner of the Building during the construction period. Accordingly, the Company has recorded project construction costs incurred by the landlord as an asset in “Property and equipment, net” and a related financing obligation in “Construction financing lease obligation” on the Company’s condensed consolidated balance sheet. The Company bifurcates its future lease payments pursuant to the 60 Binney Lease into (i) a portion that is allocated to the Building and (ii) a portion that is allocated to the land on which the Building is being constructed, which is recorded as rental expense. Although the Company estimates that the Company will not begin making lease payments pursuant to the 60 Binney Lease until April 2017, the portion of the lease obligation allocated to the land is treated for accounting purposes as an operating lease that commenced upon execution of the 60 Binney Lease in September 2015. During the three and nine months ended September 30, 2016, the Company recognized $0.5 As of September 30, 2016, Property and equipment, net, includes $ 109.7 Once the landlord completes the construction of the Building, the Company will evaluate the 60 Binney Lease in order to determine whether or not the 60 Binney Lease meets the criteria for “sale-leaseback” treatment. If the 60 Binney Lease meets the “sale-leaseback” criteria, the Company will remove the asset and the related liability from its consolidated balance sheet and treat the 60 Binney Lease as either an operating or a capital lease based on the Company’s assessment of the accounting guidance. The Company expects that upon completion of construction of the Building the 60 Binney Lease will not meet the “sale-leaseback” criteria. If the 60 Binney Lease does not meet “sale-leaseback” criteria, the Company will treat the 60 Binney Lease as a financing obligation and will depreciate the asset in accordance with the Company’s accounting policy.

Significant agreements

Significant agreements	9 Months Ended
	Sep. 30, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Significant agreements	8. Significant agreements Celgene Corporation Original Collaboration Agreement On March 19, 2013, the Company entered into a Master Collaboration Agreement (the “Collaboration Agreement”) with Celgene Corporation (“Celgene”) to discover, develop and commercialize potentially disease-altering gene therapies in oncology. The collaboration is focused on applying gene therapy technology to genetically modify a patient’s own T cells, known as chimeric antigen receptor, or CAR T cells, to target and destroy cancer cells. Additionally, on March 19, 2013, the Company entered into a Platform Technology Sublicense Agreement (the “Sublicense Agreement”) with Celgene pursuant to which the Company obtained a sublicense to certain intellectual property from Celgene, originating under Celgene’s license from Baylor College of Medicine, for use in the collaboration. Under the terms of the Collaboration Agreement, the Company received a $75.0 million up-front, non-refundable cash payment. The Company was responsible for conducting discovery, research and development activities through completion of Phase I clinical studies, if any, during the initial term of the Collaboration Agreement, or three years. The collaboration is governed by a joint steering committee (“JSC”) formed by an equal number of representatives from the Company and Celgene. The JSC, among other activities, reviews the collaboration program, reviews and evaluates product candidates and approves regulatory plans. In addition to the JSC, the Collaboration Agreement provides that the Company and Celgene each appoint representatives to a patent committee, which is responsible for managing the intellectual property developed and used during the collaboration. Amended Collaboration Agreement On June 3, 2015, the Company and Celgene amended and restated the Collaboration Agreement (the “Amended Collaboration Agreement”). Under the Amended Collaboration Agreement, the parties will now focus the collaboration exclusively on anti- B-cell maturation antigen (“BCMA”) product candidates for a new three-year term. In connection with the Amended Collaboration Agreement, the Company received an upfront, one-time, non-refundable, non-creditable payment of $25.0 million to fund research and development under the collaboration. The collaboration will continue to be governed by the JSC. Under the terms of the Amended Collaboration Agreement, for up to two product candidates selected for development under the collaboration, the Company is responsible for conducting and funding all research and development activities performed up through completion of the initial Phase I clinical study of such product candidate. On a product candidate-by-product candidate basis, up through a specified period following enrollment of the first patient in an initial Phase I clinical study for such product candidate (the “Option Period”), the Company has granted Celgene an option to obtain an exclusive worldwide license to develop and commercialize such product candidate pursuant to a written agreement, the form of which the Company has already agreed upon. In the event that Celgene exercises its option with respect to any product candidate, the Company may elect to co-develop and co-promote the product candidate in the United States, provided that, if the Company does not exercise its option co-develop and co-promote the first product candidate in-licensed by Celgene under the Amended Collaboration Agreement, then the Company will not be permitted to exercise its option to co-develop and co-promote any future product candidates under the Amended Collaboration Agreement. If Celgene elects to exercise its option to exclusively in-license a product candidate, it must pay the Company an option fee in the amount of $10.0 million for the first product candidate and $15.0 million for any additional product candidates. On February 10, 2016, Celgene exercised its option to obtain an exclusive worldwide license to develop and commercialize bb2121, the first product candidate under the Amended Collaboration Agreement, pursuant to an executed license agreement entered into by the parties on February 16, 2016 and paid the associated $10.0 million option fee. The Company may now elect to co-develop and co-promote the product candidate in the United States and will receive an additional fee in the amount of $10.0 million in the event the Company does not exercise its option to co-develop and co-promote bb2121 with Celgene. On February 17, 2016, the parties further amended the Amended Collaboration Agreement to update the timing of certain deliverables in connection with Celgene’s option exercise for the license of the bb2121 product candidate. Accounting Analysis The Company’s Amended Collaboration Agreement with Celgene contains the following deliverables: (i) research and development services, (ii) participation on the JSC, (iii) participation on the patent committee, (iv) a license to the first product candidate, (v) manufacture of vectors and associated payload for incorporation into the first optioned product candidate under the license, and (vi) participation on the JGC under the co-development and co-promotion agreement for the first optioned product candidate under the license. The license to the first product candidate was considered a deliverable at the inception of the arrangement and therefore the associated option fee was included in allocable arrangement consideration as the Company believed there was minimal risk with regard to whether Celgene will exercise the option based on the successful completion of preclinical activities and proximity of enrollment of the first patient in an initial Phase I clinical study for this product candidate. The Company determined that the obligation within the license to manufacture or have manufactured supplies of vectors and associated payloads for incorporation into the first optioned product candidate is a deliverable, consistent with the option to license the first product candidate. However, the Company determined that the options to license any additional product candidates are substantive options and therefore were not considered deliverables at execution of the Amended Collaboration Agreement. Celgene is not contractually obligated to exercise the options. Additionally, as a result of the uncertain outcome of the discovery, research and development activities, the Company is at risk with regard to whether Celgene will exercise the options to license additional product candidates. Moreover, the Company determined that the options are not priced at a significant and incremental discount. Accordingly, the options to other product candidates are not considered deliverables and the associated option fees are not included in allocable arrangement consideration. Upon execution of the Amended Collaboration Agreement in June 2015, the Company concluded that each of the three delivered elements at the inception of the agreement (research and development services, participation on the JSC and participation on the patent committee) had standalone value from the other undelivered elements. Additionally, the Amended Collaboration Agreement does not include return rights related to the collaboration term. Accordingly, each deliverable qualified as a separate unit of accounting. The Company determined that each of the delivered elements had the same period of performance (the three year term through projected initial Phase I clinical study substantial completion) and the same pattern of revenue recognition, ratably over the period of performance as there was no other discernible pattern of recognition. The Company identified the allocable arrangement consideration as the $25.0 million up-front research and development funding payment, $10.0 million option fee for the first product candidate, $20.0 million related to remaining deferred revenue from the original Collaboration Agreement, and $54.1 million of contingent revenue related to the estimated amounts that will be received from Celgene for manufacturing services. The $109.0 million total allocable arrangement consideration was allocated based on the relative estimated selling price of the separate units of accounting at the inception of the amended agreement, resulting in $17.3 million allocated to the three delivered elements at the inception of the agreement, which will be recognized over an initial three year term. The Company is required to reassess its conclusions on standalone value of deliverables upon delivery, and therefore, upon Celgene’s exercise of its option to obtain an exclusive worldwide license to develop and commercialize bb2121 in February 2016, the Company updated its assessment. The Company determined that there were no changes in standalone value of the research and development services as the option was previously determined to be non-substantive, the Company continues to have an obligation to provide research and development services for bb2121 and other product candidates, and this obligation is separate and unrelated to the execution of the license agreement. Participation on the JSC and participation on the patent committee also continue to have standalone value from the other undelivered elements as there has been no change in facts that would change this conclusion. Accordingly, each of these three deliverables continues to qualify as a separate unit of accounting. The Company determined that each of the identified deliverables that qualify as a separate unit of accounting continue to have the same period of performance (the three year term through projected initial Phase I clinical study substantial completion) and the same pattern of revenue recognition, ratably over the period of performance as there is no other discernible pattern of recognition, and therefore there is no change in the recognition of $17.3 million allocated to these three elements. As of September 30, 2016, this will continue to be recognized over a three year term that began in June 2015. However, the Company concluded that the license to bb2121 does not have standalone value from one of the undelivered elements, the post-initial Phase I the manufacture of vectors and associated payload for bb2121 under the license, because the manufacturing is essential to the license agreement. Accordingly, these two deliverables qualify as a single combined unit of accounting. The single combined unit of accounting comprised of the license to bb2121 and the manufacture of vectors and associated payload for bb2121 were allocated consideration of $91.7 million, which will begin to be recognized upon the commencement of manufacturing services for bb2121 for Celgene post-initial Phase I, not in excess of the fixed consideration and assuming other revenue recognition criteria have been met. The Company currently expects this to commence in the second half of 2017 or first half of 2018. Revenue for the combined unit of account will be recognized on a proportional performance method or ratably over the period of performance if there is no other discernible pattern of recognition. This period of performance and recognition pattern will be revisited as the development plan changes or if other events impacting the deliverables occur. The Company evaluated all of the milestones that may be received in connection with Celgene’s option to license a product candidate resulting from the collaboration. In evaluating if a milestone is substantive, the Company assesses whether: (i) the consideration is commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the delivered item(s) as a result of a specific outcome resulting from the Company’s performance to achieve the milestone, (ii) the consideration relates solely to past performance and (iii) the consideration is reasonable relative to all of the deliverables and payment terms within the arrangement. All clinical and regulatory milestones that may be received under the option to the license agreement are considered substantive on the basis of the contingent nature of the milestone, specifically reviewing factors such as the scientific, clinical, regulatory, commercial and other risks that must be overcome to achieve the milestone as well as the level of effort and investment required. Accordingly, such amounts will be recognized as revenue in full in the period in which the associated milestone is achieved, assuming all other revenue recognition criteria are met. All commercial milestones will be accounted for in the same manner as royalties and recorded as revenue upon achievement of the milestone, assuming all other revenue recognition criteria are met. During the three months ended September 30, 2016 and 2015, the Company recognized $1.6 million and $1.3 4.6 12.6 48.0

Stock-based compensation

Stock-based compensation	9 Months Ended
	Sep. 30, 2016
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-based compensation	9. Stock-based compensation In January 2016, the number of shares of common stock available for issuance under the 2013 Stock Option and Incentive Plan (“2013 Plan”) was increased by approximately 1.5 million shares as a result of the automatic increase provision of the 2013 Plan. As of September 30, 2016, the total number of shares of common stock available for issuance under the 2013 Plan was approximately 1.2 million. Stock-based compensation expense Stock-based compensation expense by award type included within the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): Three months ended September 30, Nine months ended September 30, 2016 2015 2016 2015 Stock options $ 8,294 $ 8,407 $ 26,278 $ 28,472 Restricted stock units 1,495 1,056 4,248 2,341 Employee stock purchase plan 116 66 305 198 $ 9,905 $ 9,529 $ 30,831 $ 31,011 As of September 30, 2016, the Company had $89.4 million of unrecognized stock-based compensation expense, net of estimated forfeitures, related to unvested stock options, restricted stock units and the employee stock purchase plan, which is expected to be recognized over a weighted-average period of 2.6 years. Stock-based compensation expense by classification included within the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): Three months ended September 30, Nine months ended September 30, 2016 2015 2016 2015 Research and development $ 5,399 $ 4,426 $ 15,410 $ 19,726 General and administrative 4,506 5,103 15,421 11,285 $ 9,905 $ 9,529 $ 30,831 $ 31,011 In the first quarter of 2015, the Company modified outstanding options held by its former Chief Scientific Officer in connection with the termination of his employment. The incremental value of the modification was $3.0 million. As a result of the modification, the Company recognized $0.2 million and $3.0 million of stock-based compensation expense during the three and nine months ended September 30, 2015 In the second quarter of 2015, the Company modified the vesting conditions of a stock option award held by a non-employee founder, which resulted in $6.7 million of stock-based compensation expense recognized to research and development expense during the second quarter of 2015. Stock options The following table summarizes the stock option activity under the Company’s equity award plans (shares in thousands): Shares Weighted-average exercise price per share Outstanding at December 31, 2015 3,532 $ 48.74 Granted 944 $ 50.55 Exercised (273 ) $ 11.71 Canceled or forfeited (336 ) $ 48.88 Outstanding at September 30, 2016 3,867 $ 51.74 Exercisable at September 30, 2016 1,850 $ 38.04 Vested and expected to vest at September 30, 2016 3,776 $ 51.53 Options exercisable for 0.3 3.2 Restricted stock units The following table summarizes the restricted stock unit activity under the Company’s equity award plans (shares in thousands): Shares Weighted-average grant date fair value Unvested balance at December 31, 2015 148 $ 65.79 Granted 236 $ 50.55 Vested (110 ) $ 45.57 Forfeited (20 ) $ 41.63 Unvested balance at September 30, 2016 254 $ 62.23 Employee stock purchase plan On June 3, 2013, the Company’s board of directors adopted its 2013 Employee Stock Purchase Plan (“2013 ESPP”), which was subsequently approved by its stockholders and became effective upon the closing of the Company’s IPO on June 24, 2013. The 2013 ESPP authorizes the initial issuance of up to a total of 238,000 shares 2015, and shares

Income taxes

Income taxes	9 Months Ended
	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Income taxes	10. Income taxes Deferred tax assets and deferred tax liabilities are recognized based on temporary differences between the financial reporting and tax basis of assets and liabilities using statutory rates. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all of the deferred tax assets will not be realized. Due to the uncertainty surrounding the realization of the favorable tax attributes in future tax returns, the Company has recorded a full valuation allowance against the Company’s otherwise recognizable net deferred tax assets. For the three and nine months ended September 30, 2016, the Company recognized an income tax benefit of $0.2 and $0.5

Net loss per share

Net loss per share	9 Months Ended
	Sep. 30, 2016
Earnings Per Share [Abstract]
Net loss per share	11. Net loss per share The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect (in thousands): For the three and nine months ended September 30, 2016 2015 Outstanding stock options 3,867 3,661 Restricted stock units 254 149 ESPP shares 12 3 Acquisition holdback — 94 4,133 3,907

Summary of significant accoun18

Summary of significant accounting policies and basis of presentation (Policies)	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Basis of presentation and principles of consolidation	Basis of presentation and principles of consolidation The accompanying condensed consolidated financial statements are unaudited and have been prepared by the Company in accordance with accounting principles generally accepted in the United States (“GAAP”) as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Update (“ASU”) of the Financial Accounting Standards Board (“FASB”). Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted. These interim condensed consolidated financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the interim periods ended September 30, 2016 and 2015. The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full year. These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2015, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K filed with the Securities and Exchange Commission (the “SEC”) on February 25, 2016. The accompanying condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries: Precision Genome Engineering, Inc. (“Pregenen”), bluebird bio France – SARL, bluebird bio Australia Pty Ltd., bluebird bio (UK) Ltd., bluebird bio (Bermuda) Ltd.
Summary of accounting policies	Summary of accounting policies The significant accounting policies and estimates used in the preparation of the condensed consolidated financial statements are described in the Company’s audited financial statements as of and for the year ended December 31, 2015, and the notes thereto, which are included in the Company’s Annual Report on Form 10-K. There have been no material changes in the Company’s significant accounting policies during the nine months ended September 30, 2016.
Net income (loss) per share	Net income (loss) per share Basic net income (loss) per share is calculated by dividing net income (loss) attributable to common stockholders by the weighted average number of common shares outstanding during the period. Diluted net income per share is calculated by dividing the net income attributable to common stockholders by the weighted-average number of common stock equivalent shares outstanding for the period, including any dilutive effect from outstanding stock options, unvested restricted stock, restricted stock units, employee stock purchase plan, and warrants using the treasury stock method.
Use of estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts in the financial statements and accompanying notes. Estimates are used in the following areas, among others: fair value estimates used to assess potential impairment of long-lived assets, construction financing lease obligations, contingent consideration, stock-based compensation expense, accrued expenses, revenue and income taxes. Actual results could materially differ from those estimates.
Recently issued accounting pronouncements	Recently issued accounting pronouncements In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers (“Topic 606”), which supersedes all existing revenue recognition requirements, including most industry-specific guidance. The new standard requires a company to recognize revenue when it transfers goods or services to customers in an amount that reflects the consideration that the company expects to receive for those goods or services. The new standard will be effective on January 1, 2018 and earlier application is permitted only for annual reporting periods beginning after December 15, 2016, including interim reporting periods within that reporting period. The Company is currently evaluating the potential impact that Topic 606 may have on its financial position and results of operations. In February 2016, the FASB issued ASU 2016-02, Leases , (“ASU 2016-02”) , which requires a lessee to recognize assets and liabilities on the balance sheet for operating leases and changes many key definitions, including the definition of a lease. The new standard includes a short-term lease exception for leases with a term of 12 months or less, as part of which a lessee can make an accounting policy election not to recognize lease assets and lease liabilities. Lessees will continue to differentiate between finance leases (previously referred to as capital leases) and operating leases using classification criteria that are substantially similar to the previous guidance. The new standard will be effective beginning January 1, 2019, and early adoption is permitted for public entities. The Company is currently evaluating the potential impact ASU 2016-02 may have on its financial position and results of operations. In March 2016, the FASB issued ASU 2016-09, Improvements to Employee Share-Based Payment Accounting (“ASU No. 2016-09”), which simplifies share-based payment accounting through a variety of amendments. The standard will be effective for annual reporting periods and interim periods within those annual periods, beginning after December 15, 2016, and early adoption is permitted. The Company is currently evaluating the potential impact ASU 2016-09 may have on its financial position and results of operations. In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows: Classification of Certain Cash Receipts and Cash Payments (“Topic 230”). The new standard clarifies certain aspects of the statement of cash flows, including the classification of contingent consideration payments made after a business combination and several other clarifications not currently applicable to the Company. The new standard also clarifies that an entity should determine each separately identifiable source or use within the cash receipts and cash payments on the basis of the nature of the underlying cash flows. In situations in which cash receipts and payments have aspects of more than one class of cash flows and cannot be separated by source or use, the appropriate classification should depend on the activity that is likely to be the predominant source or use of cash flows for the item. The new standard will be effective for the Company on January 1, 2018. The adoption of this standard is not expected to have a material impact on our statements of cash flows upon adoption.

Marketable Securities (Tables)

Marketable Securities (Tables)	9 Months Ended
	Sep. 30, 2016
Investments Debt And Equity Securities [Abstract]
Summary of Available for Sale Securities Held	The following table summarizes the available-for-sale securities held at September 30, 2016 and December 31, 2015 (in thousands): Description Amortized Cost Unrealized Gains Unrealized Losses Fair Value September 30, 2016 U.S. government agency securities and treasuries $ 475,344 $ 91 $ (164 ) $ 475,271 Certificates of deposit 7,200 16 — 7,216 Total $ 482,544 $ 107 $ (164 ) $ 482,487 December 31, 2015 U.S. government agency securities and treasuries $ 689,425 $ 22 $ (2,300 ) $ 687,147 Certificates of deposit 14,360 — (13 ) 14,347 Total $ 703,785 $ 22 $ (2,313 ) $ 701,494

Fair value measurements (Tables

Fair value measurements (Tables)	9 Months Ended
	Sep. 30, 2016
Fair Value Disclosures [Abstract]
Recorded Amount of Assets and Liabilities Measured at Fair Value on Recurring Basis	The following table sets forth the Company’s assets and liabilities that are measured at fair value on a recurring basis as of September 30, 2016 and December 31, 2015 (in thousands): Description Total Quoted prices in active markets (Level 1) Significant other observable inputs (Level 2) Significant unobservable inputs (Level 3) September 30, 2016 Assets: Cash and cash equivalents $ 245,154 $ 245,154 $ — $ — Marketable securities: U.S. government agency securities and treasuries 475,271 — 475,271 — Certificates of deposit 7,216 — 7,216 — Total assets $ 727,641 $ 245,154 $ 482,487 $ — Liabilities: Contingent consideration $ 7,180 $ — $ — $ 7,180 Total liabilities $ 7,180 $ — $ — $ 7,180 December 31, 2015 Assets: Cash and cash equivalents $ 164,269 $ 158,269 $ 6,000 $ — Marketable securities: U.S. government agency securities and treasuries 687,147 — 687,147 — Certificates of deposit 14,347 — 14,347 — Total assets $ 865,763 $ 158,269 $ 707,494 $ — Liabilities: Contingent consideration $ 8,665 $ — $ — $ 8,665 Total liabilities $ 8,665 $ — $ — $ 8,665
Roll-Forward of Fair Value of the Company's Contingent Consideration Obligations	The table below provides a roll-forward of fair value of the Company’s contingent consideration obligations, which include Level 3 inputs (in thousands): Nine Months Ended September 30, 2016 Beginning balance $ 8,665 Additions — Changes in fair value 3,515 Payments (5,000 ) Ending balance $ 7,180

Property and equipment, net (Ta

Property and equipment, net (Tables)	9 Months Ended
	Sep. 30, 2016
Property Plant And Equipment [Abstract]
Property and equipment	Property and equipment, net, consists of the following (in thousands): September 30, 2016 December 31, 2015 Computer equipment and software $ 1,350 $ 1,259 Office equipment 1,427 1,104 Laboratory equipment 15,273 10,520 Leasehold improvements 13,839 11,010 Construction-in-progress 110,922 65,542 Total property and equipment, gross 142,811 89,435 Less accumulated depreciation and amortization (11,074 ) (6,821 ) Total property and equipment, net $ 131,737 $ 82,614

Accrued expenses and other cu22

Accrued expenses and other current liabilities (Tables)	9 Months Ended
	Sep. 30, 2016
Payables And Accruals [Abstract]
Summary of Accrued Expenses and Other Current Liabilities	Accrued expenses and other current liabilities consist of the following (in thousands): September 30, 2016 December 31, 2015 Employee compensation $ 8,920 $ 5,935 Accrued goods and services 23,855 15,876 Accrued license and milestone fees 15,208 277 Accrued professional fees 2,103 1,014 Deferred rent, current portion 68 964 Contingent consideration, current portion 3,913 3,584 Other 605 495 Total accrued expenses and other current liabilities $ 54,672 $ 28,145

Stock-based compensation (Table

Stock-based compensation (Tables)	9 Months Ended
	Sep. 30, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Summary of Stock-Based Compensation Expense by Award Type	Stock-based compensation expense by award type included within the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): Three months ended September 30, Nine months ended September 30, 2016 2015 2016 2015 Stock options $ 8,294 $ 8,407 $ 26,278 $ 28,472 Restricted stock units 1,495 1,056 4,248 2,341 Employee stock purchase plan 116 66 305 198 $ 9,905 $ 9,529 $ 30,831 $ 31,011
Schedule of Stock-Based Compensation Expense by Classification	Stock-based compensation expense by classification included within the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands): Three months ended September 30, Nine months ended September 30, 2016 2015 2016 2015 Research and development $ 5,399 $ 4,426 $ 15,410 $ 19,726 General and administrative 4,506 5,103 15,421 11,285 $ 9,905 $ 9,529 $ 30,831 $ 31,011
Summary of Stock Option Activity Under Plan	The following table summarizes the stock option activity under the Company’s equity award plans (shares in thousands): Shares Weighted-average exercise price per share Outstanding at December 31, 2015 3,532 $ 48.74 Granted 944 $ 50.55 Exercised (273 ) $ 11.71 Canceled or forfeited (336 ) $ 48.88 Outstanding at September 30, 2016 3,867 $ 51.74 Exercisable at September 30, 2016 1,850 $ 38.04 Vested and expected to vest at September 30, 2016 3,776 $ 51.53
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Summary of Restricted Common Stock Awards	Restricted stock units The following table summarizes the restricted stock unit activity under the Company’s equity award plans (shares in thousands): Shares Weighted-average grant date fair value Unvested balance at December 31, 2015 148 $ 65.79 Granted 236 $ 50.55 Vested (110 ) $ 45.57 Forfeited (20 ) $ 41.63 Unvested balance at September 30, 2016 254 $ 62.23

Net loss per share (Tables)

Net loss per share (Tables)	9 Months Ended
	Sep. 30, 2016
Earnings Per Share [Abstract]
Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share	The following common stock equivalents were excluded from the calculation of diluted net loss per share for the periods indicated because including them would have had an anti-dilutive effect (in thousands): For the three and nine months ended September 30, 2016 2015 Outstanding stock options 3,867 3,661 Restricted stock units 254 149 ESPP shares 12 3 Acquisition holdback — 94 4,133 3,907

Description of the business - A

Description of the business - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Date of incorporation	Apr. 16, 1992

Summary of significant accoun26

Summary of significant accounting policies and basis of presentation - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2016Segment
Accounting Policies [Abstract]
Number of operating segment	1

Marketable securities - Summary

Marketable securities - Summary of Available for Sale Securities Held (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 482,544	$ 703,785
Unrealized Gains	107	22
Unrealized Losses	(164)	(2,313)
Fair Value	482,487	701,494
U.S. Government Agency Securities and Treasuries [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	475,344	689,425
Unrealized Gains	91	22
Unrealized Losses	(164)	(2,300)
Fair Value	475,271	687,147
Certificates of Deposit [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	7,200	14,360
Unrealized Gains	16
Unrealized Losses		(13)
Fair Value	$ 7,216	$ 14,347

Fair value measurements - Recor

Fair value measurements - Recorded Amount of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Assets:
Assets, fair value disclosure, recurring	$ 727,641	$ 865,763
Liabilities:
Liabilities, fair value disclosure, recurring	7,180	8,665
Contingent Consideration [Member]
Liabilities:
Liabilities, fair value disclosure, recurring	7,180	8,665
Cash and Cash Equivalents [Member]
Assets:
Assets, fair value disclosure, recurring	245,154	164,269
Certificates of Deposit [Member]
Assets:
Assets, fair value disclosure, recurring	7,216	14,347
U.S. Government Agency Securities and Treasuries [Member]
Assets:
Assets, fair value disclosure, recurring	475,271	687,147
Quoted prices in active markets (Level 1) [Member]
Assets:
Assets, fair value disclosure, recurring	245,154	158,269
Quoted prices in active markets (Level 1) [Member] | Cash and Cash Equivalents [Member]
Assets:
Assets, fair value disclosure, recurring	245,154	158,269
Significant other observable inputs (Level 2) [Member]
Assets:
Assets, fair value disclosure, recurring	482,487	707,494
Significant other observable inputs (Level 2) [Member] | Cash and Cash Equivalents [Member]
Assets:
Assets, fair value disclosure, recurring		6,000
Significant other observable inputs (Level 2) [Member] | Certificates of Deposit [Member]
Assets:
Assets, fair value disclosure, recurring	7,216	14,347
Significant other observable inputs (Level 2) [Member] | U.S. Government Agency Securities and Treasuries [Member]
Assets:
Assets, fair value disclosure, recurring	475,271	687,147
Significant unobservable inputs (Level 3) [Member]
Liabilities:
Liabilities, fair value disclosure, recurring	7,180	8,665
Significant unobservable inputs (Level 3) [Member] | Contingent Consideration [Member]
Liabilities:
Liabilities, fair value disclosure, recurring	$ 7,180	$ 8,665

Fair value measurements - Addit

Fair value measurements - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents maturities	Three months or less
Realized gain on available-for-sale securities	$ 0
Reclassification out of accumulated other comprehensive loss	0
Unrealized Loss on Securities	255,800,000	$ 638,100,000
Unrealized loss on securities, more than twelve months	0
Investments with other-than-temporary impairment	0	0
Contingent consideration, current	3,913,000	3,584,000
Contingent consideration, non current	3,267,000	$ 5,082,000
Pregenen
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent cash payments	129,000,000
Pregenen | Preclinical Milestones [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent cash payments	9,000,000
Pregenen | Clinical Milestone Payments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent cash payments	20,100,000
Pregenen | Commercial Milestones Payments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent cash payments	$ 99,900,000
Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Milestone achievement period	2,017
Milestone discount rates	9.90%
Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Milestone achievement period	2,026
Milestone discount rates	12.70%

Fair value measurements - Roll-

Fair value measurements - Roll-Forward of Fair Value of the Company's Contingent Consideration Obligations (Detail) - Significant unobservable inputs (Level 3) [Member] - Contingent consideration obligations [Member] $ in Thousands	9 Months Ended
	Sep. 30, 2016USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 8,665
Changes in fair value	3,515
Payments	(5,000)
Ending balance	$ 7,180

Property and equipment, net - P

Property and equipment, net - Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 142,811	$ 89,435
Less accumulated depreciation and amortization	(11,074)	(6,821)
Total property and equipment, net	131,737	82,614
Computer Equipment and Software [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	1,350	1,259
Office Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	1,427	1,104
Laboratory Equipment [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	15,273	10,520
Leasehold Improvements [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	13,839	11,010
Construction in Progress [Member]
Property Plant And Equipment [Line Items]
Total property and equipment, gross	$ 110,922	$ 65,542

Property and equipment, net - A

Property and equipment, net - Additional Information (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 142,811	$ 89,435
Construction cost incurred by landlord	99,991	$ 61,901
Construction In Progress 60 Binney Street [Member]
Property Plant And Equipment [Line Items]
Property and equipment, gross	109,700
Construction cost incurred by landlord	$ 100,000

Accrued expenses and other cu33

Accrued expenses and other current liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Employee compensation	$ 8,920	$ 5,935
Accrued goods and services	23,855	15,876
Accrued license and milestone fees	15,208	277
Accrued professional fees	2,103	1,014
Deferred rent, current portion	68	964
Contingent consideration, current portion	3,913	3,584
Other	605	495
Total accrued expenses and other current liabilities	$ 54,672	$ 28,145

Accrued expenses and other cu34

Accrued expenses and other current liabilities - Additional Information (Detail) $ in Millions	Sep. 30, 2016USD ($)
Research Collaboration and License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront fee payable	$ 15

Commitments and contingencies -

Commitments and contingencies - Additional Information (Detail) € in Millions	Sep. 30, 2016USD ($)	Jun. 03, 2016USD ($)	Sep. 21, 2015USD ($)ft²$ / ft²	Jun. 29, 2015USD ($)ft²	Dec. 31, 2014USD ($)	Jun. 03, 2013USD ($)ft²	Sep. 30, 2016USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2015EUR (€)	Sep. 30, 2016EUR (€)	Dec. 31, 2015USD ($)
Commitments And Contingencies Disclosure [Line Items]
Other noncurrent assets	$ 16,247,000						$ 16,247,000	$ 16,247,000			$ 10,360,000
Lease period						9 years
Lease building space | ft²						43,600
Amendment effective date						2014-06
Additional lease building space | ft²						9,900
Lease payments						$ 200,000
Increase in monthly lease payments					$ 300,000
Option to extend this lease						5 years
Contribution from the landlord towards the initial build-out of the space						$ 7,800,000
Cash-collateralized irrevocable standby letter of credit	600,000					$ 1,300,000
Lease starting date						Jun. 3, 2013
Property and equipment, gross	142,811,000						142,811,000	142,811,000			89,435,000
Construction financing lease obligation	99,991,000						99,991,000	$ 99,991,000			$ 61,901,000
Lease starting on July 13, 2015 [Member]
Commitments And Contingencies Disclosure [Line Items]
Lease period				60 months
Lease building space | ft²				15,120
Lease payments				$ 500,000
Lease starting date				Jul. 13, 2015
Early termination lease term				20 months
Operating lease description								Under the terms of the lease, the Company leased approximately 15,120 square feet starting on July 13, 2015 for $0.5 million per year in base rent, which is subject to a 3% annual rent increase plus certain operating expenses and taxes.
Operating lease, rent increase percentage				3.00%
Lease starting on January 1, 2016 [Member]
Commitments And Contingencies Disclosure [Line Items]
Lease building space | ft²				8,075
Lease payments				$ 300,000
Lease starting date				Jan. 1, 2016
Operating lease description								Under the terms of the lease, the Company has also leased an additional 8,075 square feet of office space in the same premises starting on January 1, 2016 for an additional $0.3 million per year in base rent, which is subject to a 3% annual rent increase plus certain operating expenses and taxes. The Company expects to terminate the lease by mid-2017.
Operating lease, rent increase percentage				3.00%
Strategic manufacturing agreement [Member]
Commitments And Contingencies Disclosure [Line Items]
Lease period		12 years
Lease payments		$ 5,100,000
Early termination lease term		24 months
Amount payable upon achievement of certain construction milestones		$ 12,500,000
Milestone payments made							2,000,000
Agreement termination description								The Company may terminate this agreement any time after July 1, 2016 upon payment of a one-time termination fee and up to 24 months of fixed suite and labor fees.
Strategic manufacturing agreement [Member] | Maximum [Member]
Commitments And Contingencies Disclosure [Line Items]
Additional construction payables to milestones		$ 8,000,000
Lease starting on October 1, 2016 [Member]
Commitments And Contingencies Disclosure [Line Items]
Lease period			120 months
Lease building space | ft²			253,108
Contribution from the landlord towards the initial build-out of the space			$ 42,400,000
Cash-collateralized irrevocable standby letter of credit			$ 9,200,000
Lease starting date			Oct. 1, 2016
Lease payments base annual rent			$ 18,400,000
Capital lease description								Under the terms of the 60 Binney Lease, starting on October 1, 2016, the Company will lease approximately 253,108 square feet of office and laboratory space at $72.50 per square foot per year, or $18.4 million per year in base rent, which is subject to scheduled annual rent increases of 1.75% plus certain operating expenses and taxes.
Increase in letter of credit under the terms of the lease							13,800,000
150 Second Street Lease [Member]
Commitments And Contingencies Disclosure [Line Items]
Total lease payments no longer expected to pay due to early vacation	20,600,000						20,600,000	$ 20,600,000
Lease payments no longer expected to pay due to early vacation for 2017	2,200,000						2,200,000	2,200,000
Lease payments no longer expected to pay due to early vacation for 2018	3,500,000						3,500,000	3,500,000
Lease payments no longer expected to pay due to early vacation for 2019	3,600,000						3,600,000	3,600,000
Lease payments no longer expected to pay due to early vacation for 2020	3,700,000						3,700,000	3,700,000
Lease payments no longer expected to pay due to early vacation for 2021 and thereafter	7,600,000						7,600,000	7,600,000
60 Binney Street Lease [Member] | Lease starting on October 1, 2016 [Member]
Commitments And Contingencies Disclosure [Line Items]
Annual lease rent per square foot | $ / ft²			72.50
Lease rent increase percentage			1.75%
Option to extend capital lease			10 years
Land [Member]
Commitments And Contingencies Disclosure [Line Items]
Non-cash rent expense							500,000	1,400,000
Construction In Progress 60 Binney Street [Member]
Commitments And Contingencies Disclosure [Line Items]
Property and equipment, gross	109,700,000						109,700,000	109,700,000
Construction financing lease obligation	$ 100,000,000						$ 100,000,000	100,000,000
Cash paid to the landlord								$ 0
French Credit d'Impot Recherche Program [Member]
Commitments And Contingencies Disclosure [Line Items]
Eligible percentage of research expense monetized								30.00%
Aggregate reimbursement received related to years 2013 through 2015 | €									€ 2.3
Other noncurrent assets | €										€ 0.6

Significant agreements - Additi

Significant agreements - Additional Information (Detail) - Celgene Corporation [Member] $ in Millions	Jun. 03, 2015USD ($)Deliverables	Mar. 19, 2013USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2015USD ($)	Feb. 17, 2016USD ($)	Feb. 16, 2016USD ($)	Dec. 31, 2015USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Term of collaboration agreement		3 years
First Product Candidates [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount per product eligible to be received upon achievement of specified event	$ 10
Amount paid per product upon achievement of specified event								$ 10
Additional Product Candidates [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount per product eligible to be received upon achievement of specified event	$ 15
Co-Develop and Co-Promote Options not Exercise [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount per product eligible to be received upon achievement of specified event							$ 10
Collaborative Arrangement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of deliverable | Deliverables	3
Consideration allocated to agreement					$ 109
Deferred revenue recognition period					3 years
Deferred revenue recognized			$ 1.6	$ 1.3	$ 4.6	$ 12.6
Deferred revenue			48		48				$ 41.8
Deferred revenue expected to be recognized			10.3		10.3
Collaborative Arrangement [Member] | Option Fee [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount per product eligible to be received upon achievement of specified event			10		10
Collaborative Arrangement [Member] | Delivered Elements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement, cash payment received	$ 20
Consideration allocated to agreement					17.3
Up-front Payment Arrangement [Member] | Collaborative Arrangement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement, cash payment received		$ 75			25
Up-front Payment Arrangement [Member] | Amended Collaborative Arrangement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration agreement, cash payment received	$ 25
Manufacturing Services [Member] | Collaborative Arrangement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount per product eligible to be received upon achievement of specified event			$ 91.7		91.7
Consideration allocated to agreement					$ 54.1

Stock-based compensation - Addi

Stock-based compensation - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended				9 Months Ended
	Jan. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increased number of issuance of awards under the 2013 Plan	1,500,000
Number of shares available for issuance		1,200,000				1,200,000
Stock-based compensation expense		$ 9,905	$ 9,529			$ 30,831	$ 31,011
Stock option share exercised						273,000
Proceed from option share exercised						$ 3,200
Research And Development Expense [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense		5,399	4,426			15,410	19,726
Former Chief Scientific Officer [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Incremental value on option valuation					$ 3,000
Stock-based compensation expense			200				3,000
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock- based compensation expense related to unvested stock options, restricted stock awards and employee stock purchase plan		89,400				$ 89,400
Expected weighted-average period related to unvested stock options, restricted stock awards and employee stock purchase plan						2 years 7 months 6 days
Stock-based compensation expense		8,294	8,407			$ 26,278	28,472
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock- based compensation expense related to unvested stock options, restricted stock awards and employee stock purchase plan		89,400				$ 89,400
Expected weighted-average period related to unvested stock options, restricted stock awards and employee stock purchase plan						2 years 7 months 6 days
Stock-based compensation expense		1,495	1,056			$ 4,248	2,341
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock- based compensation expense related to unvested stock options, restricted stock awards and employee stock purchase plan		89,400				$ 89,400
Expected weighted-average period related to unvested stock options, restricted stock awards and employee stock purchase plan						2 years 7 months 6 days
Stock-based compensation expense		$ 116	$ 66			$ 305	$ 198
Common shares reserved for future issuance		238,000				238,000
Shares of common stock issued under plan						18,338	10,545
Non Employee Stock Option [Member] | Research And Development Expense [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Incremental value on option valuation				$ 6,700

Stock-based compensation - Summ

Stock-based compensation - Summary of Stock-Based Compensation Expense by Award Type (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 9,905	$ 9,529	$ 30,831	$ 31,011
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	8,294	8,407	26,278	28,472
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	1,495	1,056	4,248	2,341
Employee Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 116	$ 66	$ 305	$ 198

Stock-based compensation - Sche

Stock-based compensation - Schedule of Stock-Based Compensation Expense by Classification (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 9,905	$ 9,529	$ 30,831	$ 31,011
Research And Development [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	5,399	4,426	15,410	19,726
General And Administrative [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 4,506	$ 5,103	$ 15,421	$ 11,285

Stock-based compensation - Su40

Stock-based compensation - Summary of Stock Option Activity Under Plan (Detail) shares in Thousands	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Shares
Outstanding at beginning of period | shares	3,532
Granted | shares	944
Exercised | shares	(273)
Canceled or forfeited | shares	(336)
Outstanding at end of period | shares	3,867
Exercisable at end of period | shares	1,850
Vested and expected to vest at end of period | shares	3,776
Weighted-average exercise price per share
Outstanding at beginning of period | $ / shares	$ 48.74
Granted | $ / shares	50.55
Exercised | $ / shares	11.71
Canceled or forfeited | $ / shares	48.88
Outstanding at end of period | $ / shares	51.74
Exercisable at end of period | $ / shares	38.04
Vested and expected to vest at end of period | $ / shares	$ 51.53

Stock-based compensation - Su41

Stock-based compensation - Summary of Restricted Stock Units(Detail) - Restricted Stock Units [Member] shares in Thousands	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Shares
Unvested balance at beginning of period | shares	148
Granted | shares	236
Vested | shares	(110)
Forfeited | shares	(20)
Unvested balance at end of period | shares	254
Weighted-average grant date fair value
Unvested balance at beginning of period | $ / shares	$ 65.79
Granted | $ / shares	50.55
Vested | $ / shares	45.57
Forfeited | $ / shares	41.63
Unvested balance at end of period | $ / shares	$ 62.23

Income taxes - Additional Infor

Income taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Income tax benefit	$ 178	$ (60)	$ 549	$ (60)
Income tax (benefit) expense in other comprehensive loss related to unrealized gain (loss) on available-for-sale securities	(100)		800
Accrued income tax provision	$ 200		$ 200

Net loss per share - Common Sto

Net loss per share - Common Stock Equivalents Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from the calculation of diluted net loss per share	4,133	3,907	4,133	3,907
Outstanding Stock Options [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from the calculation of diluted net loss per share	3,867	3,661	3,867	3,661
Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from the calculation of diluted net loss per share	254	149	254	149
ESPP Shares [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from the calculation of diluted net loss per share	12	3	12	3
Acquisition holdback [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from the calculation of diluted net loss per share		94		94