Synageva BioPharma 10-K 26 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Billions, except Share data, unless otherwise specified	Dec. 31, 2014	Feb. 20, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	GEVA
Entity Registrant Name	SYNAGEVA BIOPHARMA CORP
Entity Central Index Key	911326
Current Fiscal Year End Date	-19
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		36,958,276
Entity Public Float			$2.30

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$82,653	$62,137
Short-term investments	364,255	346,596
Accounts receivable	986	1,373
Prepaid expenses and other current assets	9,938	6,617
Total current assets	457,832	416,723
Property and equipment, net	31,559	17,213
Developed technology, net	2,003	3,491
Goodwill	8,535	8,535
Other assets	4,274	1,987
Total assets	504,203	447,949
Current liabilities:
Accounts payable	2,625	2,427
Accrued expenses	21,710	11,121
Deferred revenue		232
Other current liabilities	908	140
Total current liabilities	25,243	13,920
Other long term liabilities	5,721	3,828
Total liabilities	30,964	17,748
Commitments and contingencies (Note 10)
Stockholders' equity:
Common stock, par value $0.001; 60,000 shares authorized at December 31, 2014 and 2013, respectively; 33,370 and 30,768 shares issued and outstanding at December 31, 2014 and 2013, respectively	33	31
Additional paid-in capital	920,333	684,468
Accumulated other comprehensive loss	-240	-59
Accumulated deficit	-446,887	-254,239
Total stockholders' equity	473,239	430,201
Total liabilities and stockholders' equity	$504,203	$447,949

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Statement of Financial Position [Abstract]
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	60,000,000	60,000,000
Common stock, shares issued	33,370,000	30,768,000
Common stock, shares outstanding	33,370,000	30,768,000

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Royalty revenue	$6,000	$7,042	$7,023
Collaboration and license revenue	492	6,332	7,931
Total revenue	6,492	13,374	14,954
Costs and expenses:
Research and development	142,638	79,644	37,347
Selling, general and administrative	54,498	27,560	17,396
Amortization of developed technology	1,489	2,073	3,232
Total costs and expenses	198,625	109,277	57,975
Loss from operations	-192,133	-95,903	-43,021
Other (expense) income, net	-238	159
Interest income, net	263	342	72
Loss before provision for income taxes	-192,108	-95,402	-42,949
Provision for income taxes	540	48
Net loss	($192,648)	($95,450)	($42,949)
Basic and diluted net loss per share	($5.89)	($3.40)	($1.90)
Weighted average shares used in basic and diluted per share computations	32,719	28,087	22,579

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Loss (Unaudited) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net loss	($192,648)	($95,450)	($42,949)
Other comprehensive loss:
Fair market value adjustments of available for sale securities	-75	-37	15
Foreign currency translation adjustments	-106	-28	-5
Total other comprehensive (loss) gain	-181	-65	10
Comprehensive loss	($192,829)	($95,515)	($42,939)

Statements_of_Changes_in_Stock

Statements of Changes in Stockholders' Equity (USD $)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
In Thousands
Beginning balance at Dec. 31, 2011	$74,048	$18	$189,874	($115,840)	($4)
Beginning balance, shares at Dec. 31, 2011		17,582
Issuance of common stock	192,736	6	192,730
Issuance of common stock, shares		6,366
Exercise of stock options	1,361	0	1,361
Exercise of stock options, shares	519	519
Stock-based compensation expense	4,971		4,971
Fair market value adjustments of available for sale investments	15				15
Cumulative translation adjustment	-5				-5
Net loss	-42,949			-42,949
Ending Balance at Dec. 31, 2012	230,177	24	388,936	-158,789	6
Ending Balance, shares at Dec. 31, 2012		24,467
Issuance of common stock	281,193	6	281,187
Issuance of common stock, shares		5,636
Exercise of stock options	5,159	1	5,158
Exercise of stock options, shares	660	665
Stock-based compensation expense	9,187		9,187
Fair market value adjustments of available for sale investments	-37				-37
Cumulative translation adjustment	-28				-28
Net loss	-95,450			-95,450
Ending Balance at Dec. 31, 2013	430,201	31	684,468	-254,239	-59
Ending Balance, shares at Dec. 31, 2013		30,768
Issuance of common stock	200,925	2	200,923
Issuance of common stock, shares		2,000
Exercise of stock options	14,612	0	14,612
Exercise of stock options, shares	592	602
Stock-based compensation expense	20,330		20,330
Fair market value adjustments of available for sale investments	-75				-75
Cumulative translation adjustment	-106				-106
Net loss	-192,648			-192,648
Ending Balance at Dec. 31, 2014	$473,239	$33	$920,333	($446,887)	($240)
Ending Balance, shares at Dec. 31, 2014		33,370

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities
Net loss	($192,648)	($95,450)	($42,949)
Adjustments:
Depreciation and amortization	6,071	5,566	4,272
Stock compensation expense	20,330	9,187	4,971
Amortization of premium on investments	3,798	2,486	310
Impairment of equity method investment	3,488
Loss on equity method investment	616
Acquired in-process research and development		2,500	344
Changes in assets and liabilities, net of acquisition:
Accounts receivable	387	1,226	-388
Prepaid expenses, other current assets, and other assets	-3,392	-3,076	-1,324
Accounts payable	32	-149	1,069
Accrued expenses, other current and non-current liabilities	11,426	7,867	109
Deferred revenue	-232	-5,159	2,651
Net cash used in operating activities	-150,124	-75,002	-30,935
Cash flows from investing activities
Purchase of available for sale investments	-508,232	-425,999	-195,365
Proceeds from sales and maturities of available for sale investments	486,700	271,950
Purchase of equity method investment	-6,104
Capital expenditures	-16,766	-14,621	-3,746
Purchase of in-process research and development and other assets		-2,500	-394
Restricted cash	-216	-1,935
Net cash used in investing activities	-44,618	-173,105	-199,505
Cash flows from financing activities
Proceeds from issuance of common stock, net of issuance costs	200,925	281,193	192,736
Proceeds from exercise of stock options	14,612	5,159	1,361
Payments for lease financing obligation (Note 3)	-173
Net cash provided by financing activities	215,364	286,352	194,097
Effect of exchange rates on cash	-106	9	-6
Net increase (decrease) in cash and equivalents	20,516	38,254	-36,349
Cash and equivalents at the beginning of period	62,137	23,883	60,232
Cash and equivalents at the end of period	82,653	62,137	23,883
Capitalization of leasehold improvements related to facility lease obligation (Note 3)	2,388	1,713
Capital expenditures incurred but not yet paid	$321	$360

Nature_of_the_Business

Nature of the Business	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Nature of the Business	1	Nature of the Business
	Synageva BioPharma Corp. (Synageva or the Company) is a biopharmaceutical company focused on the discovery, development, and commercialization of therapeutic products for patients with rare diseases. The Company has a pipeline of protein therapeutic programs for rare diseases with unmet medical need which are currently at various stages of development. Synageva is currently planning for a global launch of our lead program, sebelipase alfa for lysosomal acid lipase deficiency (LAL Deficiency). Kanuma™ is the proposed brand name for sebelipase alfa. The Company also has an active investigational new drug application (IND) with the U.S. Food & Drug Administration (FDA) to evaluate its second program, SBC-103 a first-mover program for mucopolysaccharidosis IIIB (MPS IIIB, also known as Sanfilippo B syndrome). The Company is currently dosing patients with MPS IIIB in a Phase 1/2 study investigating intravenous administration of SBC-103 and plans to report preliminary data from this study in the second half of 2015. The Company’s third pipeline program, SBC-105, is a first-mover enzyme therapy in preclinical development for rare disorders of calcification, including the first planned indication for generalized calcification in infants (GACI). Synageva has additional first-mover and potentially bio-superior protein therapeutic pipeline programs for other rare diseases at different stages of preclinical development. Synageva owns the worldwide commercial rights to all of its pipeline programs.
	The Company’s business is subject to risks including those common to companies in the biopharmaceutical industry, such as the successful development of products, patient enrollment, clinical trial uncertainty, regulatory approval, manufacturing and supply disruption, fluctuations in operating results and financial risks, potential need for additional funding, protection of proprietary technology and patent risks, compliance with government regulations, dependence on key personnel, competition, appropriate commercial infrastructure, technological and medical risks and management of growth.
	The Company has incurred losses since inception and at December 31, 2014, had an accumulated deficit of $446.9 million. The Company expects to incur losses over the next several years as it continues to expand its drug discovery, development efforts and commercial activities. As a result of continuing losses, the Company may seek additional funding through a combination of public or private financing, collaborative relationships, licensing or other arrangements. The Company may not be able to obtain financing on acceptable terms, or at all, and the Company may not be able to enter into new collaboration or license agreements. If the Company is unable to obtain additional funding on a timely basis, it may be required to curtail or terminate some or all of its development programs and commercialization plans, including some or all of its product candidates.
	Through December 31, 2014, the Company has funded its operations primarily from proceeds of the sale of stock, and to a lesser extent, royalty income and collaboration agreements. In March 2014, the Company completed an offering of 2.0 million shares of common stock and received net proceeds of approximately $200.9 million. In addition to this financing, the Company received aggregate net proceeds of approximately $473.9 million from public equity offerings in fiscal 2013 and 2012. In January 2015, the Company completed an offering of 3.5 million shares of common stock and received net proceeds of $308.7 million. The proceeds from the January 2015 offering are not included in the consolidated financials as of December 31, 2014, as the offering occurred subsequent to year end.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2	Summary of Significant Accounting Policies
	Basis of Presentation
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Principles of Consolidation
	Synageva’s consolidated financial statements include the accounts of Synageva and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
	Reverse Merger
	On November 2, 2011, Trimeris, Inc., a Delaware corporation (Trimeris), closed a merger transaction (the Reverse Merger) with Synageva BioPharma Corp., a privately held Delaware corporation (Private Synageva), pursuant to an Agreement and Plan of Merger and Reorganization, dated as of June 13, 2011 (the Merger Agreement), by and among Trimeris, Private Synageva and Tesla Merger Sub, Inc., a wholly owned subsidiary of Trimeris (Merger Sub). Pursuant to the Merger Agreement, Private Synageva became a wholly owned subsidiary of Trimeris through a merger of Merger Sub with and into Private Synageva, and the former stockholders of Private Synageva received shares of Trimeris that constituted a majority of the outstanding shares of Trimeris. In connection with the Reverse Merger, Trimeris changed its name to Synageva BioPharma Corp.
	The Reverse Merger was accounted for as a reverse acquisition under which Private Synageva was considered the acquirer of Trimeris.
	Cash and Cash Equivalents
	The Company considers all highly liquid investments with a remaining maturity at the date of purchase of 90 days or less to be cash equivalents. At December 31, 2014 and 2013, substantially all cash equivalents were U.S. treasury bills and amounts held in money market accounts at commercial banks.
	Investments
	All of the Company’s investments were classified as available-for-sale at December 31, 2014 and 2013. The principal amounts of short-term investments are summarized in the tables below:
			Less Than 12 Months to Maturity
			Amortized			Unrealized			Unrealized			Fair Value
			Cost			Gains			(Losses)
	Balance at December 31, 2014:
	U.S. Treasury securities		$	364,352		$	—		$	(97	)	$	364,255
	Total		$	364,352		$	—		$	(97	)	$	364,255
	Balance at December 31, 2013:
	U.S. Treasury securities		$	346,618		$	—		$	(22	)	$	346,596
	Total		$	346,618		$	—		$	(22	)	$	346,596
	The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2014:
			December 31,			Quoted			Significant			Significant
			2014			Price in			Other			Unobservable
						Active			Observable			Inputs
						Markets			Inputs			(Level 3)
						(Level 1)			(Level 2)
	Assets
	Cash equivalents
	Money market fund		$	71,226		$	—		$	71,226		$	—
	US treasury securities			—			—			—			—
	Marketable securities
	US treasury securities			364,255			—			364,255			—
	Total		$	435,481		$	—		$	435,481		$	—
	Level 1 inputs are quoted prices in active markets for identical assets or liabilities and consist of cash on deposit. Items classified as Level 2 within the valuation hierarchy consist of U.S. government-related debt securities and money market funds. We estimate the fair values of these marketable securities by taking into consideration valuations obtained from third-party pricing sources. These pricing sources utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include market pricing based on real-time trade data for the same or similar securities, issuer credit spreads, benchmark yields, and other observable inputs. We validate the prices provided by our third-party pricing sources by understanding the models used, obtaining market values from other pricing sources and analyzing pricing data in certain instances.
	The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2013:
			December 31,			Quoted			Significant			Significant
			2013			Price in			Other			Unobservable
						Active			Observable			Inputs
						Markets			Inputs			(Level 3)
						(Level 1)			(Level 2)
	Assets
	Cash equivalents
	Money market fund		$	27,899		$	27,899		$	—		$	—
	US treasury securities			21,021			—			21,021			—
	Marketable securities
	US treasury securities			346,596			—			346,596			—
	Total		$	395,516		$	27,899		$	367,617		$	—
	Impairment of Other Long-Lived Assets
	The Company continually evaluates whether events or circumstances have occurred that indicate that the estimated remaining useful life of long-lived assets and intangible assets may warrant revision or if events or circumstances indicate that the carrying value of these assets may be impaired. To assess whether assets have been impaired, the estimated undiscounted future cash flows for the estimated remaining useful life of the assets are compared to the carrying value. To the extent that the future cash flows are less than the carrying value, the assets are written down to the estimated fair value, based on the discounted cash flows of the asset.
	Other-than-Temporary Impairment
	The Company assesses other-than-temporary impairment in equity method investments in accordance with ASC 323-10, “Investments—Equity Method and Joint Ventures.” Equity method investments are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an investment might not be recoverable. To evaluate potential other-than-temporary impairments, the Company: i) determines when an investment is considered impaired; ii) evaluates whether the impairment is other-than-temporary, and iii) measures and recognizes the other-than-temporary impairment. Once an equity method investment is deemed to be other-than-temporarily impaired, it is recorded at its fair value. An impairment charge is measured as the difference between the carrying amount of the asset and the fair value. As part of the Company’s impairment assessment at year end, it evaluated the strategic equity method investment made in 2014 (described below).
	Equity Method Investment
	During the second quarter of 2014, Synageva made a strategic investment in a privately-held biotechnology company focused on the development of targeted treatments for liver diseases. Under the terms of the agreement, Synageva made an initial $5.0 million non-refundable payment, which in part was used to fund preclinical development through proof of concept for an undisclosed initial program. The Company has the option to fund further preclinical development, and, upon achievement of certain development milestones for the initial program, the option to acquire the company for $28.5 million plus additional payments based on achievement of development, regulatory and revenue milestones.
	Synageva determined that this investment represents a variable interest in a variable interest entity (VIE). Variable interests in VIEs are investments or other interests that absorb portions of a VIEs expected losses or receive portions of the entity’s expected returns. According to the accounting guidance, a variable interest holder must evaluate whether it is the VIE’s primary beneficiary, to determine whether consolidation accounting is required. Only one entity can be the primary beneficiary. The Company evaluated the applicable criteria and determined that, while it may be in a position to benefit most significantly from the investment, it does not have the power to direct the activities that most significantly impact the economic performance of the VIE. The Company believes those powers reside with the management of the VIE. Therefore, the Company is not required to consolidate the VIE in its financial statements at this time. The consolidation assessment could change if significant changes to the relationship occur in the future, such as if the option to acquire is exercised. The Company also evaluated whether its involvement in the VIE provides it with “significant influence” over the investment, which determines whether to account for the investment under the equity or cost methods. The Company’s ownership percentage at the onset of the arrangement was approximately 12%, which is below the 20% presumed percentage of significant influence. However, because of the continued involvement in reviewing the progress of the development program, the Company determined that it does have a significant level of influence, as defined by the accounting guidance.
	The initial $5.0 million investment was comprised of a $1.5 million upfront cash payment and $3.5 million cash payment for Series A-1 Preferred Stock. In addition, the Company capitalized $0.6 million of direct costs associated with the investment. Additional funding of $2.0 million was made during 2014 for additional Series A-1 Preferred Stock. The $6.1 million equity method investment was adjusted based on the Company’s pro-rata share of the investment’s net income or net loss and totaled $5.5 million after accounting for Synageva’s pro-rata share of the investments net loss throughout the year.
	At year end, the Company evaluated the strategic equity method investment and determined that the asset was other-than-temporarily impaired, and that the estimated fair value of the investment was less than the carrying value of the investment. The Company determined the fair value of the asset to be $2.0 million, based on a discounted cash flows analysis of the asset. As such, the Company wrote down the asset to its fair value, resulting in incremental expense of $3.5 million for the year ended December 31, 2014. As of December 31, 2014, the equity method investment totaled $2.0 million and is included in other assets in our accompanying consolidated balance sheets. The Company has recorded approximately $3.5 million of research and development expense related to the impairment, and $0.6 million of “other expense” related to its pro rata portion of the VIEs operating losses since the investment was made. The remaining $2.0 million balance for the equity method investment represents the Company’s current maximum exposure to loss related to the asset.
	Amortization of Developed Technology
	The Company provides for amortization of developed technology, computed using an accelerated method based on the undiscounted cash flows received from the FUZEON royalty stream, in proportion to the estimated total undiscounted cash flows, as discussed in further in Note 5, “Goodwill and Intangible Assets, net”.
	Goodwill
	The difference between the purchase price and the fair value of assets acquired and liabilities assumed in a business combination is allocated to goodwill. Goodwill is not amortized; however, it is required to be tested for impairment annually. Furthermore, testing for impairment is required on an interim basis if an event or circumstance indicates that it is more likely than not an impairment loss has been incurred. An impairment loss would be recognized to the extent that the carrying amount of goodwill exceeds its implied fair value. Absent an event that indicates a specific impairment may exist, the Company has selected December 31 as the date for performing the annual goodwill impairment test.
	The Company adopted ASU No. 2011-08, Intangibles-Goodwill and Other (Topic 350): Testing Goodwill for Impairment, during fiscal 2012, which allows companies to perform a simplified goodwill impairment test. Entities are no longer required to calculate the fair value of the reporting unit unless the qualitative factors indicate that it is more likely than not that a reporting unit’s fair value is less than its carrying amount. We evaluated our goodwill using the simplified approach, and our goodwill was not impaired as of December 31, 2014.
	Revenue Recognition
The Company’s business strategy may include entering into collaborative agreements with biotechnology and pharmaceutical companies. Revenue under collaborations may include the receipt of non-refundable license fees, payments based on achievement of development objectives, reimbursement of research and development costs and royalties on product sales.
The Company recognizes revenue when all of the following criteria are met: persuasive evidence of an arrangement exists, services are performed or products are delivered, the fee is fixed and determinable, and collection is reasonably assured. Determination of whether persuasive evidence exists and whether delivery has occurred or services have been rendered are based on management’s judgment regarding the fixed nature of the fee charged for deliverables and the collectability of those fees. Should changes in conditions cause management to determine these criteria are not met for future transactions, revenue recognized could be adversely affected.
Collaboration and License Revenue
The Company recognizes revenue related to collaboration and license agreements in accordance with the provisions of ASC Topics 605-25 “Revenue Recognition—Multiple Element Arrangements” (ASC Topic 605-25). The Company determines the selling price of a deliverable using the hierarchy as prescribed in ASC Topic 605-25 based on VSOE, third party evidence “TPE,” or BESP. VSOE is based on the price charged when the element sold separately and is the price actually charged for that deliverable. TPE is determined based on third party evidence for a similar deliverable when sold separately and BESP is the price which the Company would transact a sale if the elements of the collaboration and license agreements were sold on a stand-alone basis. The Company evaluates the above noted hierarchy when determining the fair value of a deliverable. The process for determining VSOE, TPE, or BESP involves significant judgment on the part of the Company and can include considerations of multiple factors such as estimated direct expenses and other costs and available data. ASC 605-25 is effective prospectively for new arrangements or upon material modification of existing arrangements.
The Company evaluates all deliverables within an arrangement to determine whether or not they provided value on a stand-alone basis. Based on this evaluation, the deliverables are separated into units of accounting. The arrangement consideration that is fixed and determinable at the inception of the arrangement is allocated to the separate units of accounting based on the estimated selling price. The Company may exercise significant judgment in determining whether a deliverable is a separate unit of accounting as well as in estimating the selling prices of such units of accounting.
Whenever the Company determines that an arrangement should be accounted for as a single unit of accounting, it must determine the period over which the performance obligations will be performed and revenue will be recognized. Revenue will be recognized using either a proportional performance or straight-line method. The Company recognizes revenue using the proportional performance method provided that the Company can reasonably estimate the level of effort required to complete its performance obligations under an arrangement and such performance obligations are provided on a best-efforts basis. Direct labor hours or full-time equivalents are typically used as the measure of performance. Revenue recognized under the relative performance method would be determined by multiplying the total payments under the contract, excluding royalties and payments contingent upon achievement of substantive milestones, by the ratio of level of effort incurred to date to estimated total level of effort required to complete the Company’s performance obligations under the arrangement. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the relative performance method, as of each reporting period.
Significant management judgment is required in determining the level of effort required under an arrangement and the period over which the Company is expected to complete its performance obligations under an arrangement
The Company applies the guidance pursuant to ASU No. 2010-17, Revenue Recognition—Milestone Method, for all sales-based, commercial and research and development milestones achieved. Under the milestone method, a payment that is contingent upon the achievement of a substantive milestone is recognized in its entirety in the period in which the milestone is achieved. A milestone is an event (i) that can be achieved based in whole or in part on either our performance or on the occurrence of a specific outcome resulting from our performance, (ii) for which there is substantive uncertainty at the date the arrangement is entered into that the event will be achieved and (iii) that would result in additional payments being due. The determination that a milestone is substantive is subject to considerable judgment and is made at the inception of the arrangement. Milestones are considered substantive when the consideration earned from the achievement of the milestone is (i) commensurate with either the Company’s performance to achieve the milestone or the enhancement of value of the item delivered as a result of a specific outcome resulting from our performance to achieve the milestone, (ii) relates solely to past performance and (iii) is reasonable relative to all deliverables and payment terms in the arrangement. The adoption of this standard in fiscal 2011 has not impacted our financial position or results of operations.
See Note 9, “License Agreements and Collaborations,” for additional information on specific arrangements. Collaboration and license revenue totaled approximately $0.5 million, $6.3 million and $7.9 million for the years ended December 31, 2014, 2013 and 2012, respectively. The Company’s collaboration with Mitsbushi Tanabe was completed in 2013.
Royalty Revenue
Royalty revenues are recognized in the period earned, based on contract terms when reported sales are reliably measurable and collectability is reasonably assured. Following the merger with Trimeris, we received royalties due to the Development and License Agreement with Roche (the “Roche License Agreement”). As part of the Roche License Agreement, Roche has an exclusive license to manufacture and sell FUZEON worldwide and the Company receives royalty payments equal to 16% of worldwide net sales of FUZEON occurring from and after January 1, 2011. Under the Roche License Agreement, Roche may deduct from its royalty payments to us 50% of any royalties paid to third parties which are reasonably required to allow Roche to sell FUZEON in a given country, including royalties paid to Novartis Vaccines and Diagnostics, Inc. (Novartis).” To calculate the royalty revenue paid to Synageva, a 5.5% distribution charge is deducted from Roche’s reported net sales, and Synageva receives a 16% royalty on the adjusted net sales amount. Revenue from royalties totaled $6.0 million, $7.0 million, and $7.0 million for the year ended December 31, 2014, 2013 and 2012, respectively. These royalties represent the royalty payment earned from Roche based on total worldwide net sales of FUZEON since the closing of the Reverse Merger in November 2011.
Reimbursement of Costs
Reimbursement of research and development costs by third party collaborators is recognized as revenue provided the Company has determined that it is acting primarily as a principal in the transaction according to the provisions outlined in the Financial Accounting Standards Board (FASB) Codification Topic 605-45, Revenue Recognition, Principal Agent Considerations, the amounts are determinable and collection of the related receivable is reasonably assured.
Deferred Revenue
Amounts received prior to satisfying the above revenue recognition criteria are recorded as deferred revenue in the accompanying consolidated balance sheets. Amounts not expected to be recognized within twelve months from the balance sheet date would be classified as long-term deferred revenue.
Research and Development
Research and development expenses primarily consist of internal personnel expense for discovery research, pre-clinical and clinical operations, manufacturing development, medical affairs and regulatory functions as well as fees for, clinical and non-clinical studies, materials and supplies, facilities, depreciation, third-party costs for contracted services, manufacturing process improvement and testing costs, and other research and development related costs. Clinical development and manufacturing costs are a significant component of our research and development expenses. We contract with third parties that perform various clinical trial activities and outsourced manufacturing activities on our behalf in the ongoing development of our product candidates. The financial terms of these contracts are subject to negotiations and may vary from contract to contract and may result in uneven payment flow. Research and development costs are expensed as incurred if no planned alternative future use exists for the technology and if the payment is not payment for future services. The Company defers and capitalizes its nonrefundable advance payments that are for research and development activities until the related goods are delivered or the related services are performed.
Segment Reporting
The Company is managed and operated as one business, focused on the discovery, development, and commercialization of therapeutic products for patients with rare diseases for which there is a high unmet medical need. The entire business is managed by a single management team with reporting to the chief executive officer. The Company does not operate separate lines of business or separate business entities with respect to its products or product candidates. Accordingly, the Company does not prepare discrete financial information with respect to separate product areas or by location and only has one reportable segment.
Legal, Intellectual Property (IP) and Patent Costs
The Company accrues estimated liabilities for loss contingencies when it is probable that a liability has been incurred and the amount of the claim assessment or damages can be reasonably estimated. Synageva expenses legal fees, IP-related and patent costs as they are incurred.
Income Taxes
Deferred income taxes are provided for the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and operating loss carryforwards and credits. Valuation allowances are recorded to reduce the net deferred tax assets to amounts the Company believes are more-likely-than-not to be realized.
Stock-Based Compensation
The Company’s share-based compensation awards to employees, including grants of employee stock options, are valued at fair value on the date of grant, and are expensed over the requisite service period. The requisite service period is the period during which an employee is required to provide service in exchange for an award, which generally is the vesting period.
Concentration of Credit Risk and Other Risks and Uncertainties
Financial instruments that potentially subject the Company to credit risk consist principally of cash, cash equivalents and U.S. treasury securities. The Company places its cash and cash equivalents in bank deposits, money market funds, and U.S. treasury bills which are maintained at several financial institutions. Deposits in these institutions may exceed the amount of insurance provided on such deposits. Management believes it has established guidelines relative to credit quality, diversification and maturities that maintain security and liquidity.
The Company is subject to risks and uncertainties common to the biotechnology industry. Such risks and uncertainties include, but are not limited to: (a) results from current and planned clinical trials, (b) scientific data collected on the Company’s technologies currently in preclinical research and development, (c) decisions made by the FDA or other regulatory bodies with respect to the initiation of human clinical trials, (d) decisions made by the FDA or other regulatory bodies with respect to approval and commercial sale of any of the Company’s proposed products, (e) the commercial acceptance of any products approved for sale and the ability of the Company to manufacture, distribute and sell for a profit any products approved for sale, (f) the Company’s ability to obtain the necessary patents and proprietary rights to effectively protect its technologies, (g) the outcome of any collaborations or alliances entered into by the Company in the future with pharmaceutical or other biotechnology companies, (h) dependence on key personnel, (i) competition with better capitalized companies and (j) ability to raise additional funds.
Basic and Diluted Net Loss per Common Share
Basic net loss per common share has been computed by dividing net loss by the weighted average number of shares outstanding during the period. Diluted net income per share, if applicable, has been computed by dividing diluted net income by the diluted number of shares outstanding during the period. Except where the result would be antidilutive to loss from continuing operations, diluted net loss per share has been computed assuming the conversion of convertible obligations and the elimination of the related interest expense, the exercise of stock options and warrants, as well as their related income tax effects.
The following table sets forth the computation of basic and diluted net loss per common share:
		Years Ended December 31,
		2014			2013			2012
Numerator:
Net loss		$	(192,648	)	$	(95,450	)	$	(42,949	)
Denominator
Weighted average common shares
Denominator for basic calculation			32,719			28,087			22,579
Denominator for diluted calculation			32,719			28,087			22,579
Net loss per share:
Basic		$	(5.89	)	$	(3.40	)	$	(1.90	)
Diluted		$	(5.89	)	$	(3.40	)	$	(1.90	)
The Company’s potential dilutive stock options have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average common stock outstanding used to calculate both basic and diluted net loss per share are the same. The following shares of potentially dilutive securities have been excluded from the computations of diluted weighted average shares outstanding as the effect of including such securities would be antidilutive:
		As of December 31,
		2014			2013			2012
Common stock equivalents			3,286			2,710			2,529
Recently Issued and Proposed Accounting Pronouncements
In August 2014, the FASB issued Accounting Standards Update No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (ASU 2014-15). ASU 2014-15 requires management to assess an entity’s ability to continue as a going concern, and to provide related footnote disclosures in certain circumstances. The standard is effective for public entities for annual and interim periods beginning after December 15, 2016, with early adoption permitted. We are currently evaluating the provisions of ASU 2014-15 and assessing the impact, if any, it may have on our financial position, results of operations or cash flows.
In May 2014, the FASB and the International Accounting Standards Board (IASB) jointly issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09), a comprehensive new revenue recognition standard that will supersede nearly all existing revenue recognition guidance. The objective of ASU 2014-09 is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 will be effective for the first quarter of 2017. An entity can elect to adopt ASU 2014-09 using one of two methods, either full retrospective adoption to each prior reporting period, or recognizing the cumulative effect of adoption at the date of initial application. The Company is in the process of evaluating the new standard and does not know the effect, if any, ASU 2014-09 will have on the Consolidated Financial Statements or which adoption method will be used.
Accumulated Other Comprehensive Loss
The following table summarizes the changes in accumulated other comprehensive loss, net of tax by component:
		Unrealized			Translation			Total
		Loss on			Adjustments
		Available
		for Sale
		Securities
Balance, as of December 31, 2013		$	(22	)	$	(37	)	$	(59	)
Other comprehensive loss before reclassifications			(75	)		(106	)		(181	)
Net current period other comprehensive loss		$	(75	)	$	(106	)	$	(181	)
Balance, as of December 31, 2014		$	(97	)	$	(143	)	$	(240	)

Property_and_Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property and Equipment	3	Property and Equipment
	Property and equipment are recorded at cost and are depreciated and amortized using the straight-line method over the assets’ expected useful lives. Property and equipment held under capital leases and leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. Upon retirement or sale, the cost of the assets disposed of and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is credited or charged to income. Repairs and maintenance costs are expensed as incurred.
	Asset Classification		Estimated
			Useful Life
	Computer hardware and software		3 years
	Vehicles		5 years
	Furniture and fixtures		5-7 years
	Lab and facility equipment		5-7 years
	Leasehold improvements and fixed assets under financing lease		shorter of estimated
			useful life or lease term
	Occupancy Arrangements
	Bogart, GA Manufacturing Facility Lease and Buildout
	In October 2013, the Company entered into a lease agreement for two 35,000 square foot shell buildings on twelve acres in Bogart, Georgia. The landlord’s construction of the shell buildings was completed late in the second quarter of 2014. In conjunction with the construction, the Company built out the shell buildings to its specifications.
	The landlord construction and tenant improvements were made in accordance with the Company’s plans and included substantial outfitting of the building. The scope of the improvements did not qualify as “normal tenant improvements” under the lease accounting guidance. Accordingly, for accounting purposes, the Company was deemed the owner of the buildings during the construction period. As construction progressed, the Company recorded the project construction costs incurred as an asset, along with a corresponding facility lease obligation, on the balance sheet for the total amount of project costs incurred whether funded by the Company or the landlord. At the time the Company began occupying the facilities in the third quarter of 2014, it had recorded total leasehold improvements for the Bogart facility of $14.4 million, $4.1 million of which related to landlord funded construction. The Company is amortizing the facility lease obligation using the effective interest method, and reduced the facility lease obligation by $0.2 million related to payments made in the period.
	Lexington, MA Headquarters
	On February 20, 2014, the Company entered into a lease amendment to expand the currently leased corporate headquarters located at 33 Hayden Avenue, Lexington, Massachusetts by 29,316 rentable square feet. The Company began occupying the expanded space in June 2014 upon the completion of landlord building modifications. The total combined leased space, including the additional space, totals 80,872 square feet. The initial term of the amendment begins upon the Company occupying the additional space, through December 2019, concurrent with the original lease.
	The following summarizes our property and equipment balances as of December 31, 2014 and 2013:
			December 31,
			2014			2013
	Laboratory equipment		$	8,528		$	6,228
	Leasehold improvements			28,876			13,923
	Computer, software and other			3,449			2,048
	Construction in process			—			1,713
				40,853			23,912
	Less: Accumulated depreciation			(9,294	)		(6,699	)
			$	31,559		$	17,213
	Depreciation expense was $4.6 million, $3.5 million and $1.0 million for fiscal years 2014, 2013, and 2012, respectively.

Supplemental_Balance_Sheet_Dat

Supplemental Balance Sheet Data	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Balance Sheet Data	4	Supplemental Balance Sheet Data
	Prepaid expenses and other current assets consist of the following:
			December 31,
			2014		2013
	Prepaid clinical, manufacturing, and scientific costs		$	4,081	$	3,960
	Interest receivable			1,018		859
	Prepaid insurance			1,238		958
	Other			3,601		840
			$	9,938	$	6,617
	Other non-current assets consist of the following:
			December 31,
			2014		2013
	Restricted cash		$	2,151	$	1,935
	Equity method investment		$	2,000		—
	Other			123		52
			$	4,274	$	1,987
	Restricted cash relates to deposits associated with construction activities at our new Bogart, GA facility and a long-term letter of credit associated with our headquarters in Lexington, MA.
	Accrued expenses consist of the following:
			December 31,
			2014		2013
	Accrued compensation and benefits		$	6,093	$	3,244
	Clinical, manufacturing and scientific costs			12,140		6,587
	Professional fees			1,131		568
	Other			2,346		722
			$	21,710	$	11,121

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets, net	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets, net	5	Goodwill and Intangible Assets, net
	In fiscal 2011, we acquired $8.5 million of goodwill in the Reverse Merger. We have not recognized any impairment charges, nor have we acquired additional goodwill in any of the periods presented. The Company performed its annual goodwill assessment as of December 31, 2014, and notes that its goodwill is not impaired as of December 31, 2014.
	Intangible assets, net of accumulated amortization is as follows (in thousands):
					As of December 31, 2014
			Initial		Cost		Accumulated			Net
			Estimated Life				Amortization
	Developed Technology			10 years	$	9,300	$	(7,297	)	$	2,003
	The developed technology asset represents the present value of the estimated future FUZEON royalty stream. Amortization expense totaled $1.5 million, $2.1 million and $3.2 million for fiscal 2014, 2013 and 2012, respectively. The developed technology asset acquired in the Reverse Merger with Trimeris is being amortized over the estimated life of the royalty stream, in proportion to the related royalty revenue. As a result, the estimated level of amortization expense is weighted toward the earlier years. Assuming no change to our estimates of the Roche royalty stream, the Company expects amortization expense to approximate the following:
	Fiscal		Amortization
	Year		(in thousands)
	2015		$	747
	2016			490
	2017			318
	2018			207
	2019 and beyond			241

Share_Based_Payments

Share Based Payments	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share Based Payments	6	Share Based Payments
	The 2014 Equity Incentive Plan (2014 Plan) was approved by the Company’s stockholders at the Company’s annual meeting, held June 4, 2014. The 2014 Plan replaced the Company’s 2005 Stock Plan as the equity compensation plan from which the Company may make equity based awards to employees, directors and consultants. The 2014 Plan provides for the issuance of up to 2.5 million shares of the Company’s common stock, plus up to 1.0 million of additional shares if awards under the 2005 Stock Plan are cancelled or expire. Shares subject to outstanding awards under the 2005 Stock Plan and 2014 Plan totaled 1.8 million and 1.3 million, respectively, as of December 31, 2014. At December 31, 2014, there were 1.4 million shares remaining available for grant under the 2014 Plan.
	The Company uses the Black-Scholes option pricing model to measure the fair value of its option awards. The fair value of each stock option grant was estimated on the date of grant using the Black-Scholes option-pricing model. The expected life assumption is based on the limited exercise historical experience at the Company, management’s expectations based on the length of time that an employee will stay at the Company, the vesting period of four years and the contractual term of ten years. The Company estimates volatility using a blended approach encompassing: (i) historical experience and peer group (including industry, size, life cycle and financial leverage), and (ii) implied volatility from publicly traded options with the longest available contractual terms. The risk-free interest rate is based on the U.S. Treasury zero coupon rate with a remaining term approximating the expected term used as the input to the Black-Scholes option pricing model.
	The weighted average assumptions used in the option pricing model for stock option grants were as follows:
			Year Ended
			December 31,
			2014			2013			2012
	Expected dividend yield			None			None			None
	Weighted average volatility in stock price			66	%		58	%		50	%
	Weighted average risk-free interest rate			1.91	%		1.39	%		0.88	%
	Expected life of stock awards-years			6 years			6 years			6 years
	The Company also maintains an Employee Stock Purchase Plan (the ESPP), which allows eligible employees to use payroll deductions to purchase shares of the Company’s common stock at a discount of 15% to the lesser of the fair market value of the Company’s stock on (i) the date on which an employee elects to participate in the ESPP and (ii) the closing price on the last day of the ESPP option period. The plan is considered a compensatory employee stock purchase plan, results in incremental stock-based compensation expense in future periods. Option periods under the ESPP run from January 1 to June 30 and July 1 to December 31 of each year.
	The assumptions used to estimate the per share fair value of stock purchase rights granted under the ESPP were as follows:
			Year Ended
			December  31,
			2014		2013
	Expected volatility		43.4-59.0%		38.5-49.6%
	Dividend yield		0.00%		0.00%
	Expected life		6 months		6 months
	Risk-free interest rate		0.07-.10%		0.09-.12%
	A summary of stock option and restricted stock unit activity under all equity plans for the years ended December 31, 2014, 2013 and 2012 is a follows:
			Stock Options						Restricted Stock Units
			Shares			Weighted			Shares			Weighted
						Average						Average
						Exercise Price						Grant  Date
												Fair Value
	Outstanding at December 31, 2011			2,371		$	15.34			—		$	—
	Granted			820			43.9			—			—
	Exercised			(519	)		2.62			—			—
	Canceled or expired			(143	)		53.83			—			—
	Outstanding at December 31, 2012			2,529		$	25.06			—		$	—
	Granted			1,119			45.31			—			—
	Exercised			(660	)		7.52			—			—
	Canceled or expired			(278	)		60.8			—			—
	Outstanding at December 31, 2013			2,710		$	34.05			—		$	—
	Granted			1,397			80.78			30			63.11
	Exercised			(592	)		23.91			—			—
	Canceled or expired			(259	)		63.3			—			—
	Outstanding at December 31, 2014			3,256		$	53.62			30		$	63.11
	Exercisable at December 31, 2014			1,150		$	34.15			—			—
	Exercisable and expected to vest at December 31, 2014			2,940		$	52.48			30		$	63.11
	The weighted average grant date fair value of options granted in 2014, 2013 and 2012 was $48.52, $23.41 and $20.38, respectively. The total intrinsic value of stock options exercised during the years ended December 31, 2014, 2013 and 2012 was $37.4 million, $28.3 million and $21.2 million, respectively.
	Stock options outstanding and currently exercisable at December 31, 2014, under all equity plans, are as follows:
			Options Outstanding									Options Exercisable
	Range of Exercise Prices		Number			Weighted			Weighted			Number		Weighted
			Outstanding			Average			Average			Exercisable		Average
						Remaining			Exercise					Exercise
						Contractual			Price					Price
						Life (yrs)
	$0.61-$0.95			72			4.4		$	0.94			72	$	0.94
	$1.10-$1.70			103			6.4			1.7			68		1.7
	$3.52-$8.73			28			6.7			8.71			10		8.67
	$10.10-$20.60			33			4.7			13.66			33		13.67
	$23.00-$45.50			1,390			7.6			36.37			785		35.05
	$45.51-$69.50			527			8.2			59.11			155		56.6
	$69.51-$94.79			891			9.4			80.35			26		80.35
	$94.80-$194.00			212			9.6			96.06			1		97.93
				3,256			8.2		$	53.62			1,150	$	34.15
	As of December 31, 2014, the unamortized compensation expense related to outstanding unvested options approximated $70.0 million and is expected to be recognized over a weighted average period of 2.7 years. The unamortized compensation expense related to outstanding unvested restricted stock units (RSUs) approximated $1.8 million and is expected to be recognized over a weighted average period of 3.7 years.
	The aggregate intrinsic value of options and RSUs outstanding and options exercisable at December 31, 2014 is approximately $130.9 million and $67.3 million, respectively, which represents the total intrinsic value (the excess of the fair value of the Company’s stock on December 31, 2014 over the exercise price, multiplied by the number of in-the-money awards) that would have been received by the award holders had all award holders exercised their awards on December 31, 2014.
	The Company recognized stock-based compensation expense on all stock option awards as follows:
			Year Ended December 31,
			2014			2013			2012
	Research and development		$	8,694		$	3,586		$	1,432
Selling, general and administrative			11,636			5,601			3,539
		$	20,330		$	9,187		$	4,971

Defined_Contribution_Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2014
Postemployment Benefits [Abstract]
Defined Contribution Plan	7	Defined Contribution Plan
	The Company has a defined contribution plan that is intended to qualify under Section 401(k) of the Internal Revenue Code of 1986, as amended (the “Code”). All employees, except part-time employees, are eligible to participate in the plan. Participants may contribute through payroll deductions, amounts not to exceed Internal Revenue Code limitations. During the years ended December 31, 2014, 2013 and 2012, the Company recognized expense for 401(k) matching contributions of $1.1 million, $0.5 million and $0.2 million, respectively.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Taxes	8	Income Taxes
	For financial reporting purposes, loss before income taxes includes the following components for the year ended December 31:
			Year Ended December 31,
			2014			2013			2012
	U.S. pretax loss		$	(37,256	)	$	(95,588	)	$	(43,032	)
	Non-U.S. pretax (loss) income			(154,852	)		186			83
	Loss before provision for income taxes		$	(192,108	)	$	(95,402	)	$	(42,949	)
	The components of the income tax provision are as follows:
			Year Ended December 31,
			2014			2013			2012
	Domestic
	Current		$	332		$	—		$	—
	Deferred			—			—			—
				332			—			—
	Foreign
	Current			208			48			—
	Deferred			—			—			—
				208			48			—
	Total
	Current			540			48		$	—
	Deferred			—			—			—
			$	540		$	48		$	—
	The Company’s effective tax rate differs from that based on the federal statutory rate due to the following:
			Years Ended December 31,
			2014			2013			2012
	Federal tax at statutory rate			(34.0	)%		(34.0	)%		(34.0	)%
	State income taxes			0.3			(3.8	)		(2.7	)
	State rate changes			—			0.2			5
	Federal and state credits			(18.2	)		(22.2	)		(36.7	)
	Foreign rate differential			20.7			—			—
	Nondeductible 162(m) compensation			0.1			2.9			—
	Expiration of state NOLs			—			—			25.9
	Stock-based compensation			0.7			0.6			0.8
	Valuation allowance			29.5			55.7			41.6
	Other			1.2			0.7			0.1
	Provision for income taxes			0.3	%		0.1	%		—
	Significant components of the Company’s net deferred tax asset as December 31, 2014 and 2013 are as follows:
			2014			2013
	Deferred tax assets:
	Net operating losses		$	43,740		$	42,962
	Capitalized research and development			20,838			23,822
	Tax credit carryforwards			108,590			57,155
	Deferred revenue			—			87
	Accrued expenses			586			210
	Depreciation and amortization			2,660			1,787
	Stock-based compensation			7,602			3,411
	Other			1,967			11
				185,983			129,445
	Deferred tax liabilities:
	Acquired intangibles			(742	)		(655	)
	Valuation allowance			(185,241	)		(128,790	)
	Net deferred tax asset		$	—		$	—
	At December 31, 2014, the Company had federal and state net operating loss carry forwards of $131.8 million and $108.9 million, respectively, which expire at various times through 2034. The Company has federal orphan drug credits and federal and state research tax credit carryforwards of $110.3 million, available to reduce future tax liabilities. The federal orphan drug credits and federal and state research tax credits expire at various times through 2034. Approximately $52.9 million of the federal and state net operating loss carryforwards relate to deductions from stock option compensation, which are tracked separately and not included in the Company’s deferred tax asset in accordance with ASC 718. The future benefit from these deductions will be recorded as a credit to additional paid in capital to the extent they reduce taxes payable.
	Utilization of the net operating loss (NOL) and research and development (R&D) credit carry forwards may be subject to a substantial annual limitation under Section 382 of the Code due to ownership change limitations that have occurred previously or that could occur in the future. These ownership changes may limit the amount of NOL and R&D credit carry forwards that can be utilized annually to offset future taxable income and tax, respectively. As part of the Reverse Merger, the Company acquired federal tax attributes that are significantly limited under Section 382 of the Code. There also could be additional ownership changes in the future which may result in additional limitations on the utilization of NOL carryforwards and credits.
	Management has evaluated the positive and negative evidence bearing upon the realizability of its deferred tax assets, and has determined that it is more-likely-than-not that the Company will not recognize the benefits of its deferred tax asset. Accordingly, a valuation allowance of $185.2 million and $128.8 million has been established at December 31, 2014 and 2013, respectively. The increase in the valuation allowance is due to the increase in the deferred tax assets described above. The Company did not release any portion of its valuation allowance in 2014.
	The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending tax examinations.
	Below is a table of the earliest tax years that remain subject to examination by jurisdictions:
			Earliest Tax
			Year Subject to
			Examination
	Jurisdiction
	U.S Federal			2011
	State of Georgia			2011
	State of Florida			2012
State of California			2012
State of Texas			2012
Commonwealth of Massachusetts			2011
All years including and subsequent to the above years remain open to examination by the taxing authorities. Also, tax attributes carrying forward from years prior to 2011 are subject to adjustment by the Internal Revenue Service if they have been or will be used in a future period. The resolution of any tax matters is not expected to have a material effect on the Company’s financial statements. The Company’s policy is to record interest and penalties related to income taxes as part of the tax provision. There were no uncertain tax positions in 2014 and 2013.
Unrecognized Deferred Tax Liability Related to Investments in Foreign Subsidiaries
U.S. income and foreign withholding taxes have not been recognized on the excess of the amount for financial reporting over the tax basis of investments in foreign subsidiaries that is indefinitely reinvested outside the United States. This amount becomes taxable upon a repatriation of assets from the subsidiary or a sale or liquidation of the subsidiary. The amount of such temporary differences were immaterial as of December 31, 2014. In general, it is the practice and intention of the Company to reinvest the earnings of its non-U.S. subsidiaries in those operations.
Uncertain Tax Positions
Under the authoritative guidance on accounting for and disclosure of uncertainty in tax positions, the Company is required to determine whether a tax position of the Company is more likely than not to be sustained upon examination, including resolution of any related appeals of litigation processes, based on the technical merits of the position. The Company has not recorded any amounts for unrecognized tax benefits as of December 31, 2014 and 2013.
Massachusetts Life Sciences Center
In 2013, the Company received a grant totaling $0.7 million from the Massachusetts Life Sciences Center (MLSC) based on projected hiring in the state of Massachusetts in 2013. The Company recognizes the grant ratably to other income over the five year commitment period, once it is probable that the hiring commitment has been met for the applicable year. The Company recognized $0.1 million in 2014, related to the award.
In 2014, the Company received a grant totaling $0.9 million from the MLSC based on projected hiring in the state of Massachusetts in 2014. The Company recognizes the grant ratably to other income over the five year commitment period, once it is probable that the hiring commitment has been met for the applicable year. The Company recognized $0.2 million in 2014, related to the award.

License_Agreements_and_Collabo

License Agreements and Collaborations	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License Agreements and Collaborations	9	License Agreements and Collaborations
	Collaborations
	In August 2011, the Company entered into a collaboration agreement with Mitsubishi Tanabe Pharma Corporation (Mitsubishi Tanabe) whereby the Company utilizes its proprietary expression technology for the development of a certain targeted compound. The agreement included an upfront development payment to the Company of $3.0 million and on-going reimbursement or funding of development costs, estimated during the initial development period to be approximately $1.5 million.
	In March 2012, the Company entered into a second agreement with Mitsubishi Tanabe to develop a second protein therapeutic. The agreement included an upfront license payment to the Company of $9.0 million and on-going reimbursement or funding of development costs, estimated during the initial development period to be approximately $0.8 million.
	The Company evaluated the collaboration agreements in order to determine whether the deliverables at the inception of the agreements: (i) the upfront license payments, (ii) the research services during the development periods, and (iii) the JSC’s participation should be accounted for as a single unit or multiple units of accounting. The Company concluded that the upfront license payments do not have standalone value to Mitsubishi Tanabe because (i) Mitsubishi Tanabe does not have the ability to transfer or sublicense and (ii) the activities to be conducted during the development period are highly dependent on the Company’s unique knowledge and understanding of its proprietary technology which is critical to optimizing the compounds. The Company determined that the JSC is a deliverable through the development period. In both agreements, the Company concluded that there are two units of accounting which are being delivered over the same performance period. Under both agreements, we recognized revenue using the proportional performance method, which resulted in both upfront payments and reimbursed research and development payments being recognized over the development term which is our performance period. We measure our proportional performance based on the development hours incurred to date compared to the estimated total development hours.
	Revenue recognized under the first and second Mitsubishi Tanabe development programs totaled $2.0 million and $4.1 million for the year ended December 31, 2013, respectively. Revenue was recognized using the proportional performance method. As of December 31, 2013, the Company had completed its obligations under the arrangements and had recognized all remaining deferred revenue balances associated with the programs.
	Roche Collaboration
	The Roche License Agreement
	On May 25, 2011, Trimeris entered into the Roche License Agreement with Roche, pursuant to which Roche has an exclusive license to manufacture and sell FUZEON worldwide and the Company receives royalty payments equal to 16% of worldwide net sales of FUZEON occurring from and after January 1, 2011. The Roche License Agreement superseded and replaced the Prior Roche Agreements. Under the Roche License Agreement, Roche may deduct from its royalty payments to us 50% of any royalties paid to third parties which are reasonably required to allow Roche to sell FUZEON in a given country, including royalties paid to Novartis Vaccines and Diagnostics, Inc. (Novartis).” To calculate the royalty revenue paid to Synageva, a 5.5% distribution charge is deducted from Roche’s reported net sales, and Synageva receives a 16% royalty on the adjusted net sales amount. We recognized royalty revenue of $6.0 million, $7.0 million and $7.0 million for the years ended December 31, 2014, 2013 and 2012, respectively.
	Roche may terminate the Roche License Agreement as a whole or for a particular country or countries in its sole discretion with advance notice. The Roche License Agreement will effectively terminate upon expiration of the last relevant patent covering FUZEON, which is expected to occur in 2021.
	FUZEON is manufactured and distributed by Roche through Roche’s sales and distribution network throughout the world in countries where regulatory approval has been received. Roche has control over all aspects of the commercialization of FUZEON, including, but not limited to, pricing, sales force activities and promotional activities.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	10	Commitments and Contingencies
	Occupancy Arrangements
	The Company leases office, laboratory and manufacturing and research facility space under operating and capital lease agreements expiring through 2024. Certain of the leases provide for options by the Company to extend the lease for multiple periods and also provide for annual minimum increases in rent, usually based on a consumer price index or annual minimum increases.
	The following is a schedule by years of future minimum rental payments required under lease agreements that have initial or remaining non-cancelable lease terms in excess of one year as of December 31, 2014:
	Year Ending December 31,		Operating		Capital
			Leases		Leases
	2015		$	2,160	$	439
	2016			2,222		448
	2017			2,187		457
	2018			2,187		466
	2019			2,190		475
	2020 and beyond			49		2,213
	Total minimum lease payments		$	10,995	$	4,498
	Less amount representing interest					(619	)
	Present value of obligations under capital leases (1)				$	3,879
		-1	The Company’s capital lease obligation relates to the construction of a manufacturing facility in Bogart, GA. Upon the completion of the landlord construction in 2014, the Company had recorded leasehold improvements and a facility lease obligation totaling $4.1 million. The current portion of capital lease obligation was $0.4 million as of December 31, 2014.
	Rental expense for the years ended December 31, 2014, 2013 and 2012 approximated $2.1 million, $1.6 million and $1.0 million, respectively.
	UGARF License Agreement
	On April 5, 2007, the Company amended and restated its technology license agreement with the University of Georgia Research Foundation (UGARF). In consideration for exclusive worldwide rights to the same patents, know-how and related technology under the original agreement, the Company provided nine thousand shares of its common stock to UGARF in addition to sublicense royalties, if applicable, and product royalties to be payable upon future commercialization and sale of any products subject to the license. On December 3, 2013, Synageva amended and restated license agreement with UGARF again to restate and clarify certain provisions, rights and obligations under the original amended and restated license agreement. No payments have been made to UGARF in fiscal 2014, 2013 and 2012.
	Shire Human Genetics Therapies
	In 2013, we entered into a settlement agreement with Shire Human Genetics Therapies, Inc. and its affiliates (Shire) and Cincinnati Children’s Hospital Research Foundation, an operating division of Children’s Hospital Medical Center, and their respective affiliates under which the parties settled the outstanding Kanuma patent-related issues between them, including the revocation actions in the United Kingdom and France and the outstanding opposition in the European Patent Office. Simultaneously with the execution of the settlement agreement, we entered into a sublicense agreement with Shire under which we received exclusive, worldwide rights to multiple patents and patent applications owned by Cincinnati Children’s Hospital Research Foundation and its affiliates. In exchange for the settlement and the rights acquired from Shire, we paid an upfront payment of $2.5 million, and will be obligated to make two sales-based milestones (each a low single-digit million dollar payment), and low, single-digit percentage tiered royalty payments on sales of Kanuma in the U.S. and certain countries in Europe. We recognized the $2.5 million upfront license payment as in-process research and development expense in the second quarter of fiscal 2013.
	Other Licensing Agreements
	The Company has licensing and sponsored research agreements with certain scientific and research institutions. The Company incurred expenses under these agreements of less than $0.1 million for the years ended December 31, 2014, 2013 and 2012. At December 31, 2014, the Company had approximately $0.1 million of potential milestone payments or other commitments payable over the next four years under agreements that are cancelable by either party under certain circumstances. These agreements also specify the payment of certain percentage royalties based on net sales of developed technologies.

Quarterly_Financial_Data_Unaud

Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data (Unaudited)	11	Quarterly Financial Data (Unaudited)
	The following tables present quarterly consolidated statement of operations data for fiscal 2014 and 2013. The below data is unaudited but, in our opinion, reflects all adjustments necessary for a fair presentation of this data in accordance with GAAP.
			Three Months Ended
			March 31,			June 30,			September 30,			December 31,
			2014			2014			2014			2014
			(unaudited)
	Revenue		$	1,586		$	2,343		$	1,326		$	1,237
	Loss from operations			(36,476	)		(50,313	)		(48,038	)		(57,306	)
	Net loss			(36,424	)		(50,240	)		(48,319	)		(57,665	)
	Loss per share, basic and diluted		$	(1.16	)	$	(1.52	)	$	(1.46	)	$	(1.73	)
	Weighted average shares outstanding, basic and diluted			31,338			33,057			33,173			33,260
			Three Months Ended
			March 31,			June 30,			September 30,			December 31,
			2013			2013			2013			2013
			(unaudited)
	Revenue		$	5,118		$	3,413		$	1,369		$	3,474
	Loss from operations			(14,573	)		(22,190	)		(28,196	)		(30,944	)
	Net loss			(14,484	)		(22,107	)		(28,123	)		(30,736	)
	Loss per share, basic and diluted		$	(0.54	)	$	(0.81	)	$	(1.02	)	$	(1.00	)
	Weighted average shares outstanding, basic and diluted			26,826			27,280			27,491			30,751

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent Events	12	Subsequent Events
	Underwritten Public Offering
	On January 6, 2015, we announced the pricing of a $325.0 million underwritten public offering of approximately 3.5 million shares of common stock at a price of $94.19. The Company received net proceeds of approximately $308.7 million from this offering.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation
	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Principles of Consolidation
	Synageva’s consolidated financial statements include the accounts of Synageva and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
	Reverse Merger
	On November 2, 2011, Trimeris, Inc., a Delaware corporation (Trimeris), closed a merger transaction (the Reverse Merger) with Synageva BioPharma Corp., a privately held Delaware corporation (Private Synageva), pursuant to an Agreement and Plan of Merger and Reorganization, dated as of June 13, 2011 (the Merger Agreement), by and among Trimeris, Private Synageva and Tesla Merger Sub, Inc., a wholly owned subsidiary of Trimeris (Merger Sub). Pursuant to the Merger Agreement, Private Synageva became a wholly owned subsidiary of Trimeris through a merger of Merger Sub with and into Private Synageva, and the former stockholders of Private Synageva received shares of Trimeris that constituted a majority of the outstanding shares of Trimeris. In connection with the Reverse Merger, Trimeris changed its name to Synageva BioPharma Corp.
	The Reverse Merger was accounted for as a reverse acquisition under which Private Synageva was considered the acquirer of Trimeris.
Use of Estimates	Use of Estimates
	The preparation of financial statements in conformity with accounting principles generally accepted in the United States of America (GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Principles of Consolidation	Principles of Consolidation
	Synageva’s consolidated financial statements include the accounts of Synageva and its wholly owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.
Reverse Merger	Reverse Merger
	On November 2, 2011, Trimeris, Inc., a Delaware corporation (Trimeris), closed a merger transaction (the Reverse Merger) with Synageva BioPharma Corp., a privately held Delaware corporation (Private Synageva), pursuant to an Agreement and Plan of Merger and Reorganization, dated as of June 13, 2011 (the Merger Agreement), by and among Trimeris, Private Synageva and Tesla Merger Sub, Inc., a wholly owned subsidiary of Trimeris (Merger Sub). Pursuant to the Merger Agreement, Private Synageva became a wholly owned subsidiary of Trimeris through a merger of Merger Sub with and into Private Synageva, and the former stockholders of Private Synageva received shares of Trimeris that constituted a majority of the outstanding shares of Trimeris. In connection with the Reverse Merger, Trimeris changed its name to Synageva BioPharma Corp.
	The Reverse Merger was accounted for as a reverse acquisition under which Private Synageva was considered the acquirer of Trimeris.
Cash and Cash Equivalents	Cash and Cash Equivalents
	The Company considers all highly liquid investments with a remaining maturity at the date of purchase of 90 days or less to be cash equivalents. At December 31, 2014 and 2013, substantially all cash equivalents were U.S. treasury bills and amounts held in money market accounts at commercial banks.
Investments	Investments
	All of the Company’s investments were classified as available-for-sale at December 31, 2014 and 2013. The principal amounts of short-term investments are summarized in the tables below:
		Less Than 12 Months to Maturity
		Amortized			Unrealized			Unrealized			Fair Value
		Cost			Gains			(Losses)
	Balance at December 31, 2014:
	U.S. Treasury securities	$	364,352		$	—		$	(97	)	$	364,255
	Total	$	364,352		$	—		$	(97	)	$	364,255
	Balance at December 31, 2013:
	U.S. Treasury securities	$	346,618		$	—		$	(22	)	$	346,596
	Total	$	346,618		$	—		$	(22	)	$	346,596
	The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2014:
		December 31,			Quoted			Significant			Significant
		2014			Price in			Other			Unobservable
					Active			Observable			Inputs
					Markets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	Assets
	Cash equivalents
	Money market fund	$	71,226		$	—		$	71,226		$	—
	US treasury securities		—			—			—			—
	Marketable securities
	US treasury securities		364,255			—			364,255			—
	Total	$	435,481		$	—		$	435,481		$	—
	Level 1 inputs are quoted prices in active markets for identical assets or liabilities and consist of cash on deposit. Items classified as Level 2 within the valuation hierarchy consist of U.S. government-related debt securities and money market funds. We estimate the fair values of these marketable securities by taking into consideration valuations obtained from third-party pricing sources. These pricing sources utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include market pricing based on real-time trade data for the same or similar securities, issuer credit spreads, benchmark yields, and other observable inputs. We validate the prices provided by our third-party pricing sources by understanding the models used, obtaining market values from other pricing sources and analyzing pricing data in certain instances.
	The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2013:
		December 31,			Quoted			Significant			Significant
		2013			Price in			Other			Unobservable
					Active			Observable			Inputs
					Markets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	Assets
	Cash equivalents
	Money market fund	$	27,899		$	27,899		$	—		$	—
	US treasury securities		21,021			—			21,021			—
	Marketable securities
	US treasury securities		346,596			—			346,596			—
	Total	$	395,516		$	27,899		$	367,617		$	—
Impairment of Other Long-Lived Assets	Impairment of Other Long-Lived Assets
	The Company continually evaluates whether events or circumstances have occurred that indicate that the estimated remaining useful life of long-lived assets and intangible assets may warrant revision or if events or circumstances indicate that the carrying value of these assets may be impaired. To assess whether assets have been impaired, the estimated undiscounted future cash flows for the estimated remaining useful life of the assets are compared to the carrying value. To the extent that the future cash flows are less than the carrying value, the assets are written down to the estimated fair value, based on the discounted cash flows of the asset.
	Other-than-Temporary Impairment
	The Company assesses other-than-temporary impairment in equity method investments in accordance with ASC 323-10, “Investments—Equity Method and Joint Ventures.” Equity method investments are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an investment might not be recoverable. To evaluate potential other-than-temporary impairments, the Company: i) determines when an investment is considered impaired; ii) evaluates whether the impairment is other-than-temporary, and iii) measures and recognizes the other-than-temporary impairment. Once an equity method investment is deemed to be other-than-temporarily impaired, it is recorded at its fair value. An impairment charge is measured as the difference between the carrying amount of the asset and the fair value. As part of the Company’s impairment assessment at year end, it evaluated the strategic equity method investment made in 2014 (described below).
	Equity Method Investment
	During the second quarter of 2014, Synageva made a strategic investment in a privately-held biotechnology company focused on the development of targeted treatments for liver diseases. Under the terms of the agreement, Synageva made an initial $5.0 million non-refundable payment, which in part was used to fund preclinical development through proof of concept for an undisclosed initial program. The Company has the option to fund further preclinical development, and, upon achievement of certain development milestones for the initial program, the option to acquire the company for $28.5 million plus additional payments based on achievement of development, regulatory and revenue milestones.
	Synageva determined that this investment represents a variable interest in a variable interest entity (VIE). Variable interests in VIEs are investments or other interests that absorb portions of a VIEs expected losses or receive portions of the entity’s expected returns. According to the accounting guidance, a variable interest holder must evaluate whether it is the VIE’s primary beneficiary, to determine whether consolidation accounting is required. Only one entity can be the primary beneficiary. The Company evaluated the applicable criteria and determined that, while it may be in a position to benefit most significantly from the investment, it does not have the power to direct the activities that most significantly impact the economic performance of the VIE. The Company believes those powers reside with the management of the VIE. Therefore, the Company is not required to consolidate the VIE in its financial statements at this time. The consolidation assessment could change if significant changes to the relationship occur in the future, such as if the option to acquire is exercised. The Company also evaluated whether its involvement in the VIE provides it with “significant influence” over the investment, which determines whether to account for the investment under the equity or cost methods. The Company’s ownership percentage at the onset of the arrangement was approximately 12%, which is below the 20% presumed percentage of significant influence. However, because of the continued involvement in reviewing the progress of the development program, the Company determined that it does have a significant level of influence, as defined by the accounting guidance.
	The initial $5.0 million investment was comprised of a $1.5 million upfront cash payment and $3.5 million cash payment for Series A-1 Preferred Stock. In addition, the Company capitalized $0.6 million of direct costs associated with the investment. Additional funding of $2.0 million was made during 2014 for additional Series A-1 Preferred Stock. The $6.1 million equity method investment was adjusted based on the Company’s pro-rata share of the investment’s net income or net loss and totaled $5.5 million after accounting for Synageva’s pro-rata share of the investments net loss throughout the year.
	At year end, the Company evaluated the strategic equity method investment and determined that the asset was other-than-temporarily impaired, and that the estimated fair value of the investment was less than the carrying value of the investment. The Company determined the fair value of the asset to be $2.0 million, based on a discounted cash flows analysis of the asset. As such, the Company wrote down the asset to its fair value, resulting in incremental expense of $3.5 million for the year ended December 31, 2014. As of December 31, 2014, the equity method investment totaled $2.0 million and is included in other assets in our accompanying consolidated balance sheets. The Company has recorded approximately $3.5 million of research and development expense related to the impairment, and $0.6 million of “other expense” related to its pro rata portion of the VIEs operating losses since the investment was made. The remaining $2.0 million balance for the equity method investment represents the Company’s current maximum exposure to loss related to the asset.
Other-than-Temporary Impairment	Other-than-Temporary Impairment
	The Company assesses other-than-temporary impairment in equity method investments in accordance with ASC 323-10, “Investments—Equity Method and Joint Ventures.” Equity method investments are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an investment might not be recoverable. To evaluate potential other-than-temporary impairments, the Company: i) determines when an investment is considered impaired; ii) evaluates whether the impairment is other-than-temporary, and iii) measures and recognizes the other-than-temporary impairment. Once an equity method investment is deemed to be other-than-temporarily impaired, it is recorded at its fair value. An impairment charge is measured as the difference between the carrying amount of the asset and the fair value. As part of the Company’s impairment assessment at year end, it evaluated the strategic equity method investment made in 2014 (described below).
Equity Method Investment	Equity Method Investment
	During the second quarter of 2014, Synageva made a strategic investment in a privately-held biotechnology company focused on the development of targeted treatments for liver diseases. Under the terms of the agreement, Synageva made an initial $5.0 million non-refundable payment, which in part was used to fund preclinical development through proof of concept for an undisclosed initial program. The Company has the option to fund further preclinical development, and, upon achievement of certain development milestones for the initial program, the option to acquire the company for $28.5 million plus additional payments based on achievement of development, regulatory and revenue milestones.
	Synageva determined that this investment represents a variable interest in a variable interest entity (VIE). Variable interests in VIEs are investments or other interests that absorb portions of a VIEs expected losses or receive portions of the entity’s expected returns. According to the accounting guidance, a variable interest holder must evaluate whether it is the VIE’s primary beneficiary, to determine whether consolidation accounting is required. Only one entity can be the primary beneficiary. The Company evaluated the applicable criteria and determined that, while it may be in a position to benefit most significantly from the investment, it does not have the power to direct the activities that most significantly impact the economic performance of the VIE. The Company believes those powers reside with the management of the VIE. Therefore, the Company is not required to consolidate the VIE in its financial statements at this time. The consolidation assessment could change if significant changes to the relationship occur in the future, such as if the option to acquire is exercised. The Company also evaluated whether its involvement in the VIE provides it with “significant influence” over the investment, which determines whether to account for the investment under the equity or cost methods. The Company’s ownership percentage at the onset of the arrangement was approximately 12%, which is below the 20% presumed percentage of significant influence. However, because of the continued involvement in reviewing the progress of the development program, the Company determined that it does have a significant level of influence, as defined by the accounting guidance.
	The initial $5.0 million investment was comprised of a $1.5 million upfront cash payment and $3.5 million cash payment for Series A-1 Preferred Stock. In addition, the Company capitalized $0.6 million of direct costs associated with the investment. Additional funding of $2.0 million was made during 2014 for additional Series A-1 Preferred Stock. The $6.1 million equity method investment was adjusted based on the Company’s pro-rata share of the investment’s net income or net loss and totaled $5.5 million after accounting for Synageva’s pro-rata share of the investments net loss throughout the year.
	At year end, the Company evaluated the strategic equity method investment and determined that the asset was other-than-temporarily impaired, and that the estimated fair value of the investment was less than the carrying value of the investment. The Company determined the fair value of the asset to be $2.0 million, based on a discounted cash flows analysis of the asset. As such, the Company wrote down the asset to its fair value, resulting in incremental expense of $3.5 million for the year ended December 31, 2014. As of December 31, 2014, the equity method investment totaled $2.0 million and is included in other assets in our accompanying consolidated balance sheets. The Company has recorded approximately $3.5 million of research and development expense related to the impairment, and $0.6 million of “other expense” related to its pro rata portion of the VIEs operating losses since the investment was made. The remaining $2.0 million balance for the equity method investment represents the Company’s current maximum exposure to loss related to the asset.
Amortization of Developed Technology	Amortization of Developed Technology
	The Company provides for amortization of developed technology, computed using an accelerated method based on the undiscounted cash flows received from the FUZEON royalty stream, in proportion to the estimated total undiscounted cash flows, as discussed in further in Note 5, “Goodwill and Intangible Assets, net”.
Goodwill	Goodwill
	The difference between the purchase price and the fair value of assets acquired and liabilities assumed in a business combination is allocated to goodwill. Goodwill is not amortized; however, it is required to be tested for impairment annually. Furthermore, testing for impairment is required on an interim basis if an event or circumstance indicates that it is more likely than not an impairment loss has been incurred. An impairment loss would be recognized to the extent that the carrying amount of goodwill exceeds its implied fair value. Absent an event that indicates a specific impairment may exist, the Company has selected December 31 as the date for performing the annual goodwill impairment test.
	The Company adopted ASU No. 2011-08, Intangibles-Goodwill and Other (Topic 350): Testing Goodwill for Impairment, during fiscal 2012, which allows companies to perform a simplified goodwill impairment test. Entities are no longer required to calculate the fair value of the reporting unit unless the qualitative factors indicate that it is more likely than not that a reporting unit’s fair value is less than its carrying amount. We evaluated our goodwill using the simplified approach, and our goodwill was not impaired as of December 31, 2014.
Revenue Recognition	Revenue Recognition
	The Company’s business strategy may include entering into collaborative agreements with biotechnology and pharmaceutical companies. Revenue under collaborations may include the receipt of non-refundable license fees, payments based on achievement of development objectives, reimbursement of research and development costs and royalties on product sales.
	The Company recognizes revenue when all of the following criteria are met: persuasive evidence of an arrangement exists, services are performed or products are delivered, the fee is fixed and determinable, and collection is reasonably assured. Determination of whether persuasive evidence exists and whether delivery has occurred or services have been rendered are based on management’s judgment regarding the fixed nature of the fee charged for deliverables and the collectability of those fees. Should changes in conditions cause management to determine these criteria are not met for future transactions, revenue recognized could be adversely affected.
Collaboration and License Revenue	Collaboration and License Revenue
	The Company recognizes revenue related to collaboration and license agreements in accordance with the provisions of ASC Topics 605-25 “Revenue Recognition—Multiple Element Arrangements” (ASC Topic 605-25). The Company determines the selling price of a deliverable using the hierarchy as prescribed in ASC Topic 605-25 based on VSOE, third party evidence “TPE,” or BESP. VSOE is based on the price charged when the element sold separately and is the price actually charged for that deliverable. TPE is determined based on third party evidence for a similar deliverable when sold separately and BESP is the price which the Company would transact a sale if the elements of the collaboration and license agreements were sold on a stand-alone basis. The Company evaluates the above noted hierarchy when determining the fair value of a deliverable. The process for determining VSOE, TPE, or BESP involves significant judgment on the part of the Company and can include considerations of multiple factors such as estimated direct expenses and other costs and available data. ASC 605-25 is effective prospectively for new arrangements or upon material modification of existing arrangements.
	The Company evaluates all deliverables within an arrangement to determine whether or not they provided value on a stand-alone basis. Based on this evaluation, the deliverables are separated into units of accounting. The arrangement consideration that is fixed and determinable at the inception of the arrangement is allocated to the separate units of accounting based on the estimated selling price. The Company may exercise significant judgment in determining whether a deliverable is a separate unit of accounting as well as in estimating the selling prices of such units of accounting.
	Whenever the Company determines that an arrangement should be accounted for as a single unit of accounting, it must determine the period over which the performance obligations will be performed and revenue will be recognized. Revenue will be recognized using either a proportional performance or straight-line method. The Company recognizes revenue using the proportional performance method provided that the Company can reasonably estimate the level of effort required to complete its performance obligations under an arrangement and such performance obligations are provided on a best-efforts basis. Direct labor hours or full-time equivalents are typically used as the measure of performance. Revenue recognized under the relative performance method would be determined by multiplying the total payments under the contract, excluding royalties and payments contingent upon achievement of substantive milestones, by the ratio of level of effort incurred to date to estimated total level of effort required to complete the Company’s performance obligations under the arrangement. Revenue is limited to the lesser of the cumulative amount of payments received or the cumulative amount of revenue earned, as determined using the relative performance method, as of each reporting period.
	Significant management judgment is required in determining the level of effort required under an arrangement and the period over which the Company is expected to complete its performance obligations under an arrangement
	The Company applies the guidance pursuant to ASU No. 2010-17, Revenue Recognition—Milestone Method, for all sales-based, commercial and research and development milestones achieved. Under the milestone method, a payment that is contingent upon the achievement of a substantive milestone is recognized in its entirety in the period in which the milestone is achieved. A milestone is an event (i) that can be achieved based in whole or in part on either our performance or on the occurrence of a specific outcome resulting from our performance, (ii) for which there is substantive uncertainty at the date the arrangement is entered into that the event will be achieved and (iii) that would result in additional payments being due. The determination that a milestone is substantive is subject to considerable judgment and is made at the inception of the arrangement. Milestones are considered substantive when the consideration earned from the achievement of the milestone is (i) commensurate with either the Company’s performance to achieve the milestone or the enhancement of value of the item delivered as a result of a specific outcome resulting from our performance to achieve the milestone, (ii) relates solely to past performance and (iii) is reasonable relative to all deliverables and payment terms in the arrangement. The adoption of this standard in fiscal 2011 has not impacted our financial position or results of operations.
	See Note 9, “License Agreements and Collaborations,” for additional information on specific arrangements. Collaboration and license revenue totaled approximately $0.5 million, $6.3 million and $7.9 million for the years ended December 31, 2014, 2013 and 2012, respectively. The Company’s collaboration with Mitsbushi Tanabe was completed in 2013.
Royalty Revenue	Royalty Revenue
	Royalty revenues are recognized in the period earned, based on contract terms when reported sales are reliably measurable and collectability is reasonably assured. Following the merger with Trimeris, we received royalties due to the Development and License Agreement with Roche (the “Roche License Agreement”). As part of the Roche License Agreement, Roche has an exclusive license to manufacture and sell FUZEON worldwide and the Company receives royalty payments equal to 16% of worldwide net sales of FUZEON occurring from and after January 1, 2011. Under the Roche License Agreement, Roche may deduct from its royalty payments to us 50% of any royalties paid to third parties which are reasonably required to allow Roche to sell FUZEON in a given country, including royalties paid to Novartis Vaccines and Diagnostics, Inc. (Novartis).” To calculate the royalty revenue paid to Synageva, a 5.5% distribution charge is deducted from Roche’s reported net sales, and Synageva receives a 16% royalty on the adjusted net sales amount. Revenue from royalties totaled $6.0 million, $7.0 million, and $7.0 million for the year ended December 31, 2014, 2013 and 2012, respectively. These royalties represent the royalty payment earned from Roche based on total worldwide net sales of FUZEON since the closing of the Reverse Merger in November 2011.
Reimbursement of Costs	Reimbursement of Costs
	Reimbursement of research and development costs by third party collaborators is recognized as revenue provided the Company has determined that it is acting primarily as a principal in the transaction according to the provisions outlined in the Financial Accounting Standards Board (FASB) Codification Topic 605-45, Revenue Recognition, Principal Agent Considerations, the amounts are determinable and collection of the related receivable is reasonably assured.
Deferred Revenue	Deferred Revenue
	Amounts received prior to satisfying the above revenue recognition criteria are recorded as deferred revenue in the accompanying consolidated balance sheets. Amounts not expected to be recognized within twelve months from the balance sheet date would be classified as long-term deferred revenue.
Research and Development	Research and Development
	Research and development expenses primarily consist of internal personnel expense for discovery research, pre-clinical and clinical operations, manufacturing development, medical affairs and regulatory functions as well as fees for, clinical and non-clinical studies, materials and supplies, facilities, depreciation, third-party costs for contracted services, manufacturing process improvement and testing costs, and other research and development related costs. Clinical development and manufacturing costs are a significant component of our research and development expenses. We contract with third parties that perform various clinical trial activities and outsourced manufacturing activities on our behalf in the ongoing development of our product candidates. The financial terms of these contracts are subject to negotiations and may vary from contract to contract and may result in uneven payment flow. Research and development costs are expensed as incurred if no planned alternative future use exists for the technology and if the payment is not payment for future services. The Company defers and capitalizes its nonrefundable advance payments that are for research and development activities until the related goods are delivered or the related services are performed.
Segment Reporting	Segment Reporting
	The Company is managed and operated as one business, focused on the discovery, development, and commercialization of therapeutic products for patients with rare diseases for which there is a high unmet medical need. The entire business is managed by a single management team with reporting to the chief executive officer. The Company does not operate separate lines of business or separate business entities with respect to its products or product candidates. Accordingly, the Company does not prepare discrete financial information with respect to separate product areas or by location and only has one reportable segment.
Legal, Intellectual Property ("IP") and Patent Costs	Legal, Intellectual Property (IP) and Patent Costs
	The Company accrues estimated liabilities for loss contingencies when it is probable that a liability has been incurred and the amount of the claim assessment or damages can be reasonably estimated. Synageva expenses legal fees, IP-related and patent costs as they are incurred.
Income Taxes	Income Taxes
	Deferred income taxes are provided for the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes and operating loss carryforwards and credits. Valuation allowances are recorded to reduce the net deferred tax assets to amounts the Company believes are more-likely-than-not to be realized.
Stock-Based Compensation	Stock-Based Compensation
	The Company’s share-based compensation awards to employees, including grants of employee stock options, are valued at fair value on the date of grant, and are expensed over the requisite service period. The requisite service period is the period during which an employee is required to provide service in exchange for an award, which generally is the vesting period.
Concentration of Credit Risk and Other Risks and Uncertainties	Concentration of Credit Risk and Other Risks and Uncertainties
	Financial instruments that potentially subject the Company to credit risk consist principally of cash, cash equivalents and U.S. treasury securities. The Company places its cash and cash equivalents in bank deposits, money market funds, and U.S. treasury bills which are maintained at several financial institutions. Deposits in these institutions may exceed the amount of insurance provided on such deposits. Management believes it has established guidelines relative to credit quality, diversification and maturities that maintain security and liquidity.
	The Company is subject to risks and uncertainties common to the biotechnology industry. Such risks and uncertainties include, but are not limited to: (a) results from current and planned clinical trials, (b) scientific data collected on the Company’s technologies currently in preclinical research and development, (c) decisions made by the FDA or other regulatory bodies with respect to the initiation of human clinical trials, (d) decisions made by the FDA or other regulatory bodies with respect to approval and commercial sale of any of the Company’s proposed products, (e) the commercial acceptance of any products approved for sale and the ability of the Company to manufacture, distribute and sell for a profit any products approved for sale, (f) the Company’s ability to obtain the necessary patents and proprietary rights to effectively protect its technologies, (g) the outcome of any collaborations or alliances entered into by the Company in the future with pharmaceutical or other biotechnology companies, (h) dependence on key personnel, (i) competition with better capitalized companies and (j) ability to raise additional funds.
Basic and Diluted Net Loss per Common Share	Basic and Diluted Net Loss per Common Share
	Basic net loss per common share has been computed by dividing net loss by the weighted average number of shares outstanding during the period. Diluted net income per share, if applicable, has been computed by dividing diluted net income by the diluted number of shares outstanding during the period. Except where the result would be antidilutive to loss from continuing operations, diluted net loss per share has been computed assuming the conversion of convertible obligations and the elimination of the related interest expense, the exercise of stock options and warrants, as well as their related income tax effects.
	The following table sets forth the computation of basic and diluted net loss per common share:
		Years Ended December 31,
		2014			2013			2012
	Numerator:
	Net loss	$	(192,648	)	$	(95,450	)	$	(42,949	)
	Denominator
	Weighted average common shares
	Denominator for basic calculation		32,719			28,087			22,579
	Denominator for diluted calculation		32,719			28,087			22,579
	Net loss per share:
	Basic	$	(5.89	)	$	(3.40	)	$	(1.90	)
	Diluted	$	(5.89	)	$	(3.40	)	$	(1.90	)
	The Company’s potential dilutive stock options have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted-average common stock outstanding used to calculate both basic and diluted net loss per share are the same. The following shares of potentially dilutive securities have been excluded from the computations of diluted weighted average shares outstanding as the effect of including such securities would be antidilutive:
		As of December 31,
		2014			2013			2012
	Common stock equivalents		3,286			2,710			2,529
Recently Issued and Proposed Accounting Pronouncements	Recently Issued and Proposed Accounting Pronouncements
	In August 2014, the FASB issued Accounting Standards Update No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern (ASU 2014-15). ASU 2014-15 requires management to assess an entity’s ability to continue as a going concern, and to provide related footnote disclosures in certain circumstances. The standard is effective for public entities for annual and interim periods beginning after December 15, 2016, with early adoption permitted. We are currently evaluating the provisions of ASU 2014-15 and assessing the impact, if any, it may have on our financial position, results of operations or cash flows.
	In May 2014, the FASB and the International Accounting Standards Board (IASB) jointly issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09), a comprehensive new revenue recognition standard that will supersede nearly all existing revenue recognition guidance. The objective of ASU 2014-09 is that a company will recognize revenue when it transfers promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 will be effective for the first quarter of 2017. An entity can elect to adopt ASU 2014-09 using one of two methods, either full retrospective adoption to each prior reporting period, or recognizing the cumulative effect of adoption at the date of initial application. The Company is in the process of evaluating the new standard and does not know the effect, if any, ASU 2014-09 will have on the Consolidated Financial Statements or which adoption method will be used.
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss
	The following table summarizes the changes in accumulated other comprehensive loss, net of tax by component:
		Unrealized			Translation			Total
		Loss on			Adjustments
		Available
		for Sale
		Securities
	Balance, as of December 31, 2013	$	(22	)	$	(37	)	$	(59	)
	Other comprehensive loss before reclassifications		(75	)		(106	)		(181	)
	Net current period other comprehensive loss	$	(75	)	$	(106	)	$	(181	)
	Balance, as of December 31, 2014	$	(97	)	$	(143	)	$	(240	)

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Amortized Cost and Estimated Fair Values	The principal amounts of short-term investments are summarized in the tables below:
		Less Than 12 Months to Maturity
		Amortized			Unrealized			Unrealized			Fair Value
		Cost			Gains			(Losses)
	Balance at December 31, 2014:
	U.S. Treasury securities	$	364,352		$	—		$	(97	)	$	364,255
	Total	$	364,352		$	—		$	(97	)	$	364,255
	Balance at December 31, 2013:
	U.S. Treasury securities	$	346,618		$	—		$	(22	)	$	346,596
	Total	$	346,618		$	—		$	(22	)	$	346,596
Financial Assets and Liabilities Measured at Fair Value on Recurring Basis
	The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2014:
		December 31,			Quoted			Significant			Significant
		2014			Price in			Other			Unobservable
					Active			Observable			Inputs
					Markets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	Assets
	Cash equivalents
	Money market fund	$	71,226		$	—		$	71,226		$	—
	US treasury securities		—			—			—			—
	Marketable securities
	US treasury securities		364,255			—			364,255			—
	Total	$	435,481		$	—		$	435,481		$	—
	The following table presents information about the Company’s financial assets and liabilities measured at fair value on a recurring basis as of December 31, 2013:
		December 31,			Quoted			Significant			Significant
		2013			Price in			Other			Unobservable
					Active			Observable			Inputs
					Markets			Inputs			(Level 3)
					(Level 1)			(Level 2)
	Assets
	Cash equivalents
	Money market fund	$	27,899		$	27,899		$	—		$	—
	US treasury securities		21,021			—			21,021			—
	Marketable securities
	US treasury securities		346,596			—			346,596			—
	Total	$	395,516		$	27,899		$	367,617		$	—
Computation of Basic and Diluted Net Loss Per Common Share	The following table sets forth the computation of basic and diluted net loss per common share:
		Years Ended December 31,
		2014			2013			2012
	Numerator:
	Net loss	$	(192,648	)	$	(95,450	)	$	(42,949	)
	Denominator
	Weighted average common shares
	Denominator for basic calculation		32,719			28,087			22,579
	Denominator for diluted calculation		32,719			28,087			22,579
	Net loss per share:
	Basic	$	(5.89	)	$	(3.40	)	$	(1.90	)
	Diluted	$	(5.89	)	$	(3.40	)	$	(1.90	)
Computations of Diluted Weighted Average Shares Outstanding	The following shares of potentially dilutive securities have been excluded from the computations of diluted weighted average shares outstanding as the effect of including such securities would be antidilutive:
		As of December 31,
		2014			2013			2012
	Common stock equivalents		3,286			2,710			2,529
Component of Changes in Accumulated Other Comprehensive Loss, Net of Tax	The following table summarizes the changes in accumulated other comprehensive loss, net of tax by component:
		Unrealized			Translation			Total
		Loss on			Adjustments
		Available
		for Sale
		Securities
	Balance, as of December 31, 2013	$	(22	)	$	(37	)	$	(59	)
	Other comprehensive loss before reclassifications		(75	)		(106	)		(181	)
	Net current period other comprehensive loss	$	(75	)	$	(106	)	$	(181	)
	Balance, as of December 31, 2014	$	(97	)	$	(143	)	$	(240	)

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Estimated Useful Life of the Related Asset
	Asset Classification	Estimated
		Useful Life
	Computer hardware and software	3 years
	Vehicles	5 years
	Furniture and fixtures	5-7 years
	Lab and facility equipment	5-7 years
	Leasehold improvements and fixed assets under financing lease	shorter of estimated
		useful life or lease term
Summary of Property and Equipment
	The following summarizes our property and equipment balances as of December 31, 2014 and 2013:
		December 31,
		2014			2013
	Laboratory equipment	$	8,528		$	6,228
	Leasehold improvements		28,876			13,923
	Computer, software and other		3,449			2,048
	Construction in process		—			1,713
			40,853			23,912
	Less: Accumulated depreciation		(9,294	)		(6,699	)
		$	31,559		$	17,213

Supplemental_Balance_Sheet_Dat1

Supplemental Balance Sheet Data (Tables)	12 Months Ended
	Dec. 31, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Summary of Prepaid Expenses and Other Current Assets	Prepaid expenses and other current assets consist of the following:
		December 31,
		2014		2013
	Prepaid clinical, manufacturing, and scientific costs	$	4,081	$	3,960
	Interest receivable		1,018		859
	Prepaid insurance		1,238		958
	Other		3,601		840
		$	9,938	$	6,617
Summary of Other Non-Current Assets	Other non-current assets consist of the following:
		December 31,
		2014		2013
	Restricted cash	$	2,151	$	1,935
	Equity method investment	$	2,000		—
	Other		123		52
		$	4,274	$	1,987
Accrued Expenses	Accrued expenses consist of the following:
		December 31,
		2014		2013
	Accrued compensation and benefits	$	6,093	$	3,244
	Clinical, manufacturing and scientific costs		12,140		6,587
	Professional fees		1,131		568
	Other		2,346		722
		$	21,710	$	11,121

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets, net (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets, Net of Accumulated Amortization	Intangible assets, net of accumulated amortization is as follows (in thousands):
				As of December 31, 2014
		Initial		Cost		Accumulated			Net
		Estimated Life				Amortization
	Developed Technology		10 years	$	9,300	$	(7,297	)	$	2,003
Expected Amortization Expense for the Next Four Fiscal Years	Assuming no change to our estimates of the Roche royalty stream, the Company expects amortization expense to approximate the following:
	Fiscal	Amortization
	Year	(in thousands)
	2015	$	747
	2016		490
	2017		318
	2018		207
	2019 and beyond		241

Share_Based_Payments_Tables

Share Based Payments (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Weighted Average Assumptions Used in the Option Pricing Model for Stock Option Grants	The weighted average assumptions used in the option pricing model for stock option grants were as follows:
		Year Ended
		December 31,
		2014			2013			2012
	Expected dividend yield		None			None			None
	Weighted average volatility in stock price		66	%		58	%		50	%
	Weighted average risk-free interest rate		1.91	%		1.39	%		0.88	%
	Expected life of stock awards-years		6 years			6 years			6 years
Assumptions Used to Estimate Per Share Fair Value of Stock Purchase Rights Granted Under ESPP	The assumptions used to estimate the per share fair value of stock purchase rights granted under the ESPP were as follows:
		Year Ended
		December  31,
		2014		2013
	Expected volatility	43.4-59.0%		38.5-49.6%
	Dividend yield	0.00%		0.00%
	Expected life	6 months		6 months
	Risk-free interest rate	0.07-.10%		0.09-.12%
Summary of Stock Option and Restricted Stock Unit Activity under all Equity Plans	A summary of stock option and restricted stock unit activity under all equity plans for the years ended December 31, 2014, 2013 and 2012 is a follows:
		Stock Options						Restricted Stock Units
		Shares			Weighted			Shares			Weighted
					Average						Average
					Exercise Price						Grant  Date
											Fair Value
	Outstanding at December 31, 2011		2,371		$	15.34			—		$	—
	Granted		820			43.9			—			—
	Exercised		(519	)		2.62			—			—
	Canceled or expired		(143	)		53.83			—			—
	Outstanding at December 31, 2012		2,529		$	25.06			—		$	—
	Granted		1,119			45.31			—			—
	Exercised		(660	)		7.52			—			—
	Canceled or expired		(278	)		60.8			—			—
	Outstanding at December 31, 2013		2,710		$	34.05			—		$	—
	Granted		1,397			80.78			30			63.11
	Exercised		(592	)		23.91			—			—
	Canceled or expired		(259	)		63.3			—			—
	Outstanding at December 31, 2014		3,256		$	53.62			30		$	63.11
	Exercisable at December 31, 2014		1,150		$	34.15			—			—
	Exercisable and expected to vest at December 31, 2014		2,940		$	52.48			30		$	63.11
Options Outstanding and Currently Exercisable	Stock options outstanding and currently exercisable at December 31, 2014, under all equity plans, are as follows:
		Options Outstanding									Options Exercisable
	Range of Exercise Prices	Number			Weighted			Weighted			Number		Weighted
		Outstanding			Average			Average			Exercisable		Average
					Remaining			Exercise					Exercise
					Contractual			Price					Price
					Life (yrs)
	$0.61-$0.95		72			4.4		$	0.94			72	$	0.94
	$1.10-$1.70		103			6.4			1.7			68		1.7
	$3.52-$8.73		28			6.7			8.71			10		8.67
	$10.10-$20.60		33			4.7			13.66			33		13.67
	$23.00-$45.50		1,390			7.6			36.37			785		35.05
	$45.51-$69.50		527			8.2			59.11			155		56.6
	$69.51-$94.79		891			9.4			80.35			26		80.35
	$94.80-$194.00		212			9.6			96.06			1		97.93
			3,256			8.2		$	53.62			1,150	$	34.15
Recognized Stock-Based Compensation Expense on all Stock Option Awards	The Company recognized stock-based compensation expense on all stock option awards as follows:
		Year Ended December 31,
		2014			2013			2012
	Research and development	$	8,694		$	3,586		$	1,432
	Selling, general and administrative		11,636			5,601			3,539
		$	20,330		$	9,187		$	4,971

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Components of Loss before Income Taxes	For financial reporting purposes, loss before income taxes includes the following components for the year ended December 31:
		Year Ended December 31,
		2014			2013			2012
	U.S. pretax loss	$	(37,256	)	$	(95,588	)	$	(43,032	)
	Non-U.S. pretax (loss) income		(154,852	)		186			83
	Loss before provision for income taxes	$	(192,108	)	$	(95,402	)	$	(42,949	)
Components of Income Tax Provision	The components of the income tax provision are as follows:
		Year Ended December 31,
		2014			2013			2012
	Domestic
	Current	$	332		$	—		$	—
	Deferred		—			—			—
			332			—			—
	Foreign
	Current		208			48			—
	Deferred		—			—			—
			208			48			—
	Total
	Current		540			48		$	—
	Deferred		—			—			—
		$	540		$	48		$	—
Schedule of Effective Tax Rate Based on Federal Statutory Rate	The Company’s effective tax rate differs from that based on the federal statutory rate due to the following:
		Years Ended December 31,
		2014			2013			2012
	Federal tax at statutory rate		(34.0	)%		(34.0	)%		(34.0	)%
	State income taxes		0.3			(3.8	)		(2.7	)
	State rate changes		—			0.2			5
	Federal and state credits		(18.2	)		(22.2	)		(36.7	)
	Foreign rate differential		20.7			—			—
	Nondeductible 162(m) compensation		0.1			2.9			—
	Expiration of state NOLs		—			—			25.9
	Stock-based compensation		0.7			0.6			0.8
	Valuation allowance		29.5			55.7			41.6
	Other		1.2			0.7			0.1
	Provision for income taxes		0.3	%		0.1	%		—
Significant Components of Net Deferred Tax Asset	Significant components of the Company’s net deferred tax asset as December 31, 2014 and 2013 are as follows:
		2014			2013
	Deferred tax assets:
	Net operating losses	$	43,740		$	42,962
	Capitalized research and development		20,838			23,822
	Tax credit carryforwards		108,590			57,155
	Deferred revenue		—			87
	Accrued expenses		586			210
	Depreciation and amortization		2,660			1,787
	Stock-based compensation		7,602			3,411
	Other		1,967			11
			185,983			129,445
	Deferred tax liabilities:
	Acquired intangibles		(742	)		(655	)
	Valuation allowance		(185,241	)		(128,790	)
	Net deferred tax asset	$	—		$	—
Schedule of Earliest Tax Years that Remain Subject to Examination by Jurisdictions	Below is a table of the earliest tax years that remain subject to examination by jurisdictions:
		Earliest Tax
		Year Subject to
		Examination
	Jurisdiction
	U.S Federal		2011
	State of Georgia		2011
	State of Florida		2012
	State of California		2012
	State of Texas		2012
	Commonwealth of Massachusetts		2011

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Minimum Future Rentals Under Non-Cancelable Leases	The following is a schedule by years of future minimum rental payments required under lease agreements that have initial or remaining non-cancelable lease terms in excess of one year as of December 31, 2014:
	Year Ending December 31,		Operating		Capital
			Leases		Leases
	2015		$	2,160	$	439
	2016			2,222		448
	2017			2,187		457
	2018			2,187		466
	2019			2,190		475
	2020 and beyond			49		2,213
	Total minimum lease payments		$	10,995	$	4,498
	Less amount representing interest					(619	)
	Present value of obligations under capital leases (1)				$	3,879
		-1	The Company’s capital lease obligation relates to the construction of a manufacturing facility in Bogart, GA. Upon the completion of the landlord construction in 2014, the Company had recorded leasehold improvements and a facility lease obligation totaling $4.1 million. The current portion of capital lease obligation was $0.4 million as of December 31, 2014.

Quarterly_Financial_Data_Unaud1

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Consolidated Statement of Operations Data	The following tables present quarterly consolidated statement of operations data for fiscal 2014 and 2013. The below data is unaudited but, in our opinion, reflects all adjustments necessary for a fair presentation of this data in accordance with GAAP.
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2014			2014			2014			2014
		(unaudited)
	Revenue	$	1,586		$	2,343		$	1,326		$	1,237
	Loss from operations		(36,476	)		(50,313	)		(48,038	)		(57,306	)
	Net loss		(36,424	)		(50,240	)		(48,319	)		(57,665	)
	Loss per share, basic and diluted	$	(1.16	)	$	(1.52	)	$	(1.46	)	$	(1.73	)
	Weighted average shares outstanding, basic and diluted		31,338			33,057			33,173			33,260
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2013			2013			2013			2013
		(unaudited)
	Revenue	$	5,118		$	3,413		$	1,369		$	3,474
	Loss from operations		(14,573	)		(22,190	)		(28,196	)		(30,944	)
	Net loss		(14,484	)		(22,107	)		(28,123	)		(30,736	)
	Loss per share, basic and diluted	$	(0.54	)	$	(0.81	)	$	(1.02	)	$	(1.00	)
	Weighted average shares outstanding, basic and diluted		26,826			27,280			27,491			30,751

Nature_of_the_Business_Additio

Nature of the Business - Additional Information (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 31, 2015	Mar. 31, 2014
Share data in Millions, unless otherwise specified
Nature Of Business [Line Items]
Accumulated deficit	($446,887,000)	($254,239,000)
Net proceeds from public offering		473,900,000	473,900,000
Subsequent Event [Member]
Nature Of Business [Line Items]
Shares of common stock offered				3.5
Net proceeds from public offering				308,700,000
Public Offering Closing on March 2014 [Member]
Nature Of Business [Line Items]
Shares of common stock offered					2
Net proceeds from public offering					$200,900,000

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
		Segment
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Maturity period of highly liquid investments		90 days
Initial non-refundable payment to fund preclinical development	$5,000,000
Additional non-refundable payment to fund preclinical development		2,000,000
Upfront cash payment		1,500,000
Direct costs capitalized		600,000
Equity method investment being amortized		6,100,000
Pro-rata share of investment's net income		-616,000
Development milestones for the initial program	28,500,000
Fair value of the asset		2,000,000
Fair value of assets resulting in incremental expense		3,500,000
Equity method investment included in other assets		2,000,000
Research and development expense related to the impairment		142,638,000	79,644,000	37,347,000
Portion of other expense related to pro rata of the VIEs operating losses		600,000
Equity method investment		2,000,000
Collaboration and license revenue		492,000	6,332,000	7,931,000
Royalty revenue		6,000,000	7,042,000	7,023,000
Number of Business segment		1
Number of reportable segment		1
Roche License Agreement [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Percentage of royalty payment received on net adjusted sales		16.00%
Percentage of royalty payment to third parties		50.00%
Percentage of Distribution charge deducted from net sales		5.50%
Royalty revenue		6,000,000	7,000,000	7,000,000
Minimum [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Company's ownership percentage		12.00%
Maximum [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Company's ownership percentage		20.00%
Impairment [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Research and development expense related to the impairment		3,500,000
Series A-1 Preferred Stock [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Cash payment for preferred stock		3,500,000
Pro-Rata Share [Member]
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Pro-rata share of investment's net income		$5,500,000

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Summary of Amortized Cost and Estimated Fair Values (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$364,352	$346,618
Unrealized Gains	0	0
Unrealized (Losses)	-97	-22
Fair Value	364,255	346,596
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	364,352	346,618
Unrealized Gains	0	0
Unrealized (Losses)	-97	-22
Fair Value	$364,255	$346,596

Summary_of_Significant_Account5

Summary of Significant Accounting Policies - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets
Marketable securities	$364,255	$346,596
Assets	435,481	395,516
Money Market Fund [Member]
Assets
Cash equivalents-money market fund	71,226	27,899
U.S. Treasury Securities [Member]
Assets
Cash equivalents-money market fund		21,021
US Treasury Securities Marketable Securities [Member]
Assets
Marketable securities	364,255	346,596
Quoted Price in Active Markets (Level 1) [Member]
Assets
Assets		27,899
Quoted Price in Active Markets (Level 1) [Member] | Money Market Fund [Member]
Assets
Cash equivalents-money market fund		27,899
Significant Other Observable Inputs (Level 2) [Member]
Assets
Assets	435,481	367,617
Significant Other Observable Inputs (Level 2) [Member] | Money Market Fund [Member]
Assets
Cash equivalents-money market fund	71,226
Significant Other Observable Inputs (Level 2) [Member] | U.S. Treasury Securities [Member]
Assets
Cash equivalents-money market fund		21,021
Significant Other Observable Inputs (Level 2) [Member] | US Treasury Securities Marketable Securities [Member]
Assets
Marketable securities	$364,255	$346,596

Summary_of_Significant_Account6

Summary of Significant Accounting Policies - Computation of Basic and Diluted Net Loss Per Common Share (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Numerator:
Net loss	($57,665)	($48,319)	($50,240)	($36,424)	($30,736)	($28,123)	($22,107)	($14,484)	($192,648)	($95,450)	($42,949)
Denominator
Weighted average common shares, Denominator for basic calculation									32,719	28,087	22,579
Weighted average common shares, Denominator for diluted calculation									32,719	28,087	22,579
Net loss per share:
Basic									($5.89)	($3.40)	($1.90)
Diluted									($5.89)	($3.40)	($1.90)

Summary_of_Significant_Account7

Summary of Significant Accounting Policies - Computations of Diluted Weighted Average Shares Outstanding (Detail) (Equity Option [Member])	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share, amount	3,286	2,710	2,529

Summary_of_Significant_Account8

Summary of Significant Accounting Policies - Component of Changes in Accumulated Other Comprehensive Loss, Net of Tax (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	($59)
Other comprehensive income (loss) before reclassifications	-181
Net current period other comprehensive loss	-181	-65	10
Ending, balance	-240	-59
Unrealized Loss on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	-22
Other comprehensive income (loss) before reclassifications	-75
Net current period other comprehensive loss	-75
Ending, balance	-97
Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	-37
Other comprehensive income (loss) before reclassifications	-106
Net current period other comprehensive loss	-106
Ending, balance	($143)

Property_and_Equipment_Estimat

Property and Equipment - Estimated Useful Life of the Related Asset (Detail)	12 Months Ended
	Dec. 31, 2014
Computer Hardware and Software [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Vehicles [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Leasehold Improvements and Fixed Assets Under Financing Lease [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	shorter of estimated useful life or lease term
Minimum [Member] | Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Minimum [Member] | Lab and Facility Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	5 years
Maximum [Member] | Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years
Maximum [Member] | Lab and Facility Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years

Property_and_Equipment_Additio

Property and Equipment - Additional information (Detail) (USD $)	1 Months Ended	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Oct. 31, 2013	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 20, 2014
	Buildings					sqft
	acre
Property, Plant and Equipment [Line Items]
Number of shell buildings under lease agreement	2
Leased space	12
Reduction in facility lease obligation		$0.20
Depreciation and amortization expense			4.6	3.5	1
Bogart Facility [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Recorded total leasehold improvements		14.4
Landlord Funded Construction [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Recorded total leasehold improvements		$4.10
Building [Member]
Property, Plant and Equipment [Line Items]
Leased space	35,000
Building [Member] | Lexington MA Headquarters [Member]
Property, Plant and Equipment [Line Items]
Leased space						80,872
Building [Member] | Lexington MA Headquarters [Member] | Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Leased space						29,316

Property_and_Equipment_Summary

Property and Equipment - Summary of Property and Equipment (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	$40,853	$23,912
Less: Accumulated depreciation and amortization	-9,294	-6,699
Property plant and equipment, Net	31,559	17,213
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	8,528	6,228
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	28,876	13,923
Computer, Software and Other [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross	3,449	2,048
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property plant and equipment, gross		$1,713

Supplemental_Balance_Sheet_Dat2

Supplemental Balance Sheet Data - Summary of Prepaid Expenses and Other Current Assets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Prepaid clinical, manufacturing, and scientific costs	$4,081	$3,960
Interest receivable	1,018	859
Prepaid insurance	1,238	958
Other	3,601	840
Total	$9,938	$6,617

Supplemental_Balance_Sheet_Dat3

Supplemental Balance Sheet Data - Summary of Other Non-Current Assets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Restricted cash	$2,151	$1,935
Equity method investment	2,000
Other	123	52
Other assets	$4,274	$1,987

Supplemental_Balance_Sheet_Dat4

Supplemental Balance Sheet Data - Accrued Expenses (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Accrued compensation and benefits	$6,093	$3,244
Clinical, manufacturing and scientific costs	12,140	6,587
Professional fees	1,131	568
Other	2,346	722
Accrued liabilities, current	$21,710	$11,121

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets, Net - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill acquired				$8,500,000
Goodwill impairment losses	0
Amortization of developed technology	$1,489,000	$2,073,000	$3,232,000

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets, Net - Intangible Assets, Net of Accumulated Amortization (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Acquired Finite-Lived Intangible Assets [Line Items]
Net	$2,003	$3,491
Developed Technology [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Initial Estimated Life	10 years
Cost	9,300
Accumulated Amortization	-7,297
Net	$2,003

Goodwill_and_Intangible_Assets4

Goodwill and Intangible Assets, Net - Expected Amortization Expense for the Next Four Fiscal Years (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Goodwill and Intangible Assets Disclosure [Abstract]
2015	$747
2016	490
2017	318
2018	207
2019 and beyond	$241

Share_Based_Payments_Additiona

Share Based Payments - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Shares subject to outstanding awards under the plan	3,256,000	2,710,000	2,529,000	2,371,000
Vesting period	4 years
Contractual term	10 years
Treasury stock coupon rate	0.00%
Weighted average grant date fair value of options granted	$48.52	$23.41	$20.38
Total intrinsic value of stock options exercised	$37.40	$28.30	$21.20
Unamortized compensation expense	70
Weighted average period	2 years 8 months 12 days
Aggregate intrinsic value of shares outstanding	130.9
Aggregate intrinsic value of shares exercisable	67.3
Restricted Stock Units [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Unamortized compensation expense	$1.80
Weighted average period	3 years 8 months 12 days
2014 Equity Incentive Plan [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Issuance of common stock	2,500,000
Shares subject to outstanding awards under the plan	1,300,000
Shares available for grant under the plan	1,400,000
2014 Equity Incentive Plan [Member] | Maximum [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Additional number of shares of common stock available for issuance	1,000,000
2005 Stock Plan [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Shares subject to outstanding awards under the plan	1,800,000
Employee Stock Purchase Plan [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]
Common stock at a discount	15.00%
Employee stock purchase plan option period, description	Option periods under the ESPP run from January 1 to June 30 and July 1 to December 31 of each year.

Share_Based_Payments_Weighted_

Share Based Payments - Weighted Average Assumptions Used in the Option Pricing Model for Stock Option Grants (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected dividend yield	0.00%	0.00%	0.00%
Weighted average volatility in stock price	66.00%	58.00%	50.00%
Weighted average risk-free interest rate	1.91%	1.39%	0.88%
Expected life of stock awards-years	6 years	6 years	6 years

Share_Based_Payments_Assumptio

Share Based Payments - Assumptions Used to Estimate Per Share Fair Value of Stock Purchase Rights Granted Under ESPP (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%	0.00%
Expected life	6 years	6 years	6 years
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, minimum	43.40%	38.50%
Expected volatility, maximum	59.00%	49.60%
Dividend yield	0.00%	0.00%
Expected life	6 months	6 months
Risk-free interest rate, minimum	0.07%	0.09%
Risk-free interest rate, maximum	0.10%	0.12%

Share_Based_Payments_Summary_o

Share Based Payments - Summary of Stock Option Activity and Restricted Stock Unit under all Equity Plans (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Stock Option Activity [Line Items]
Beginning balance, Shares	2,710	2,529	2,371
Granted, Shares	1,397	1,119	820
Exercised, Shares	-592	-660	-519
Canceled or expired, Shares	-259	-278	-143
Ending balance, Shares	3,256	2,710	2,529
Beginning balance, Weighted Average Exercise Price	$34.05	$25.06	$15.34
Granted, Weighted Average Exercise Price	$80.78	$45.31	$43.90
Exercised, Weighted Average Exercise Price	$23.91	$7.52	$2.62
Canceled or expired, Weighted Average Exercise Price	$63.30	$60.80	$53.83
Ending balance, Weighted Average Exercise Price	$53.62	$34.05	$25.06
Exercisable, Weighted Average Exercise Price	$34.15
Exercisable and expected to vest, Weighted Average Exercise Price	$52.48
Exercisable and expected to vest, Weighted Average Exercise Price	$52.48
Exercisable, Number of Shares	1,150
Exercisable and expected to vest, Number of Shares	2,940
Exercisable and expected to vest, Number of Shares	2,940
Restricted Stock Units [Member]
Schedule Of Stock Option Activity [Line Items]
Exercisable and expected to vest, Weighted Average Exercise Price	$63.11
Granted, Shares	30
Exercisable and expected to vest, Weighted Average Exercise Price	$63.11
Exercised, Shares	0	0	0
Canceled or expired, Shares	0	0	0
Ending balance, Shares	30
Granted, Weighted Average Grant Date Fair Value	$63.11
Exercised, Weighted Average Grant Date Fair Value	$0	$0	$0
Canceled or expired, Weighted Average Grant Date Fair Value	$0	$0	$0
Ending balance, Weighted Average Grant Date Fair Value	$63.11
Exercisable and expected to vest, Number of Shares	30
Exercisable and expected to vest, Number of Shares	30

Share_Based_Payments_Options_O

Share Based Payments - Options Outstanding and Currently Exercisable (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Options Outstanding	3,256
Weighted Average Remaining Contractual Life (yrs)	8 years 2 months 12 days
Weighted Average Exercise Price, Options Outstanding	$53.62
Number of Options Exercisable	1,150
Weighted Average Exercise Price, Options Exercisable	$34.15
$ 0.61 - $ 0.95 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, Lower Range Limit	$0.61
Exercise Price Range, Upper Range Limit	$0.95
Number of Options Outstanding	72
Weighted Average Remaining Contractual Life (yrs)	4 years 4 months 24 days
Weighted Average Exercise Price, Options Outstanding	$0.94
Number of Options Exercisable	72
Weighted Average Exercise Price, Options Exercisable	$0.94
$ 1.10 - $ 1.70 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, Lower Range Limit	$1.10
Exercise Price Range, Upper Range Limit	$1.70
Number of Options Outstanding	103
Weighted Average Remaining Contractual Life (yrs)	6 years 4 months 24 days
Weighted Average Exercise Price, Options Outstanding	$1.70
Number of Options Exercisable	68
Weighted Average Exercise Price, Options Exercisable	$1.70
$ 3.52 - $ 8.73 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, Lower Range Limit	$3.52
Exercise Price Range, Upper Range Limit	$8.73
Number of Options Outstanding	28
Weighted Average Remaining Contractual Life (yrs)	6 years 8 months 12 days
Weighted Average Exercise Price, Options Outstanding	$8.71
Number of Options Exercisable	10
Weighted Average Exercise Price, Options Exercisable	$8.67
$ 10.10 - $ 20.60 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, Lower Range Limit	$10.10
Exercise Price Range, Upper Range Limit	$20.60
Number of Options Outstanding	33
Weighted Average Remaining Contractual Life (yrs)	4 years 8 months 12 days
Weighted Average Exercise Price, Options Outstanding	$13.66
Number of Options Exercisable	33
Weighted Average Exercise Price, Options Exercisable	$13.67
$ 23.00 - $ 45.50 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, Lower Range Limit	$23
Exercise Price Range, Upper Range Limit	$45.50
Number of Options Outstanding	1,390
Weighted Average Remaining Contractual Life (yrs)	7 years 7 months 6 days
Weighted Average Exercise Price, Options Outstanding	$36.37
Number of Options Exercisable	785
Weighted Average Exercise Price, Options Exercisable	$35.05
$ 45.51 - $ 69.50 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, Lower Range Limit	$45.51
Exercise Price Range, Upper Range Limit	$69.50
Number of Options Outstanding	527
Weighted Average Remaining Contractual Life (yrs)	8 years 2 months 12 days
Weighted Average Exercise Price, Options Outstanding	$59.11
Number of Options Exercisable	155
Weighted Average Exercise Price, Options Exercisable	$56.60
$69.51-$94.79 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, Lower Range Limit	$69.51
Exercise Price Range, Upper Range Limit	$94.79
Number of Options Outstanding	891
Weighted Average Remaining Contractual Life (yrs)	9 years 4 months 24 days
Weighted Average Exercise Price, Options Outstanding	$80.35
Number of Options Exercisable	26
Weighted Average Exercise Price, Options Exercisable	$80.35
$94.80 - $194.00 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise Price Range, Lower Range Limit	$94.80
Exercise Price Range, Upper Range Limit	$194
Number of Options Outstanding	212
Weighted Average Remaining Contractual Life (yrs)	9 years 7 months 6 days
Weighted Average Exercise Price, Options Outstanding	$96.06
Number of Options Exercisable	1
Weighted Average Exercise Price, Options Exercisable	$97.93

Share_Based_Payments_Recognize

Share Based Payments - Recognized Stock-Based Compensation Expense on all Stock Option Awards (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total operating expenses	$20,330	$9,187	$4,971
Research and Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total operating expenses	8,694	3,586	1,432
Selling, General and Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total operating expenses	$11,636	$5,601	$3,539

Defined_Contribution_Plan_Addi

Defined Contribution Plan - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Postemployment Benefits [Abstract]
Defined contribution plan recognized expense to qualify for internal revenue code	$1.10	$0.50	$0.20

Income_Taxes_Components_of_Los

Income Taxes - Components of Loss before Income Taxes (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
U.S. pretax loss	($37,256)	($95,588)	($43,032)
Non-U.S. pretax (loss) income	-154,852	186	83
Loss before provision for income taxes	($192,108)	($95,402)	($42,949)

Income_Taxes_Components_of_Inc

Income Taxes - Components of Income Tax Provision (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Current	$332
Deferred	0	0	0
Domestic, Total	332
Current	208	48
Deferred	0	0	0
Foreign, Total	208	48
Current	540	48
Deferred	0	0	0
Total	$540	$48

Income_Taxes_Schedule_of_Effec

Income Taxes - Schedule of Effective Tax Rate Based on Federal Statutory Rate (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
Federal tax at statutory rate	-34.00%	-34.00%	-34.00%
State income taxes	0.30%	-3.80%	-2.70%
State rate changes		0.20%	5.00%
Federal and state credits	-18.20%	-22.20%	-36.70%
Foreign rate differential	20.70%
Nondeductible 162(m) compensation	0.10%	2.90%
Expiration of state NOLs			25.90%
Stock-based compensation	0.70%	0.60%	0.80%
Valuation allowance	29.50%	55.70%	41.60%
Other	1.20%	0.70%	0.10%
Provision for income taxes	0.30%	0.10%

Income_Taxes_Significant_Compo

Income Taxes - Significant Components of Net Deferred Tax Asset (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred tax assets:
Net operating losses	$43,740	$42,962
Capitalized research and development	20,838	23,822
Tax credit carryforwards	108,590	57,155
Deferred revenue		87
Accrued expenses	586	210
Depreciation and amortization	2,660	1,787
Stock-based compensation	7,602	3,411
Other	1,967	11
Deferred tax assets	185,983	129,445
Deferred tax liabilities:
Acquired intangibles	-742	-655
Valuation allowance	-185,241	-128,790
Net deferred tax asset	$0	$0

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Operating Loss Carryforwards [Line Items]
Federal net operating loss carry forwards	$131,800,000
State net operating loss carry forwards	108,900,000
Operating loss carryforwards related to deductions from stock option compensation	52,900,000
Valuation allowance	185,241,000	128,790,000
Uncertain tax positions	0	0
Amounts for unrecognized tax benefits	0	0
Massachusetts Life Sciences Center [Member]
Operating Loss Carryforwards [Line Items]
Amount received based on projected hiring	900,000	700,000
Period of recognized grant income	5 years	5 years
Amount recognized, related to award	200,000	100,000
Research Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Federal and state research tax credit	$110,300,000
Federal Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards expiration year	2034
State Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards expiration year	2034

Income_Taxes_Schedule_of_Earli

Income Taxes - Schedule of Earliest Tax Years that Remain Subject to Examination by Jurisdictions (Detail)	12 Months Ended
	Dec. 31, 2014
U.S Federal [Member]
Income Tax Examination [Line Items]
Earliest tax years that remain subject to examination by jurisdictions	2011
State of Georgia [Member]
Income Tax Examination [Line Items]
Earliest tax years that remain subject to examination by jurisdictions	2011
State of Florida [Member]
Income Tax Examination [Line Items]
Earliest tax years that remain subject to examination by jurisdictions	2012
State of California [Member]
Income Tax Examination [Line Items]
Earliest tax years that remain subject to examination by jurisdictions	2012
State of Texas [Member]
Income Tax Examination [Line Items]
Earliest tax years that remain subject to examination by jurisdictions	2012
Commonwealth of Massachusetts [Member]
Income Tax Examination [Line Items]
Earliest tax years that remain subject to examination by jurisdictions	2011

License_Agreements_and_Collabo1

License Agreements and Collaborations - Additional Information (Detail) (USD $)	3 Months Ended								12 Months Ended			0 Months Ended	1 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	25-May-11	Mar. 31, 2012	Aug. 31, 2011
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized under the first total	$1,237,000	$1,326,000	$2,343,000	$1,586,000	$3,474,000	$1,369,000	$3,413,000	$5,118,000	$6,492,000	$13,374,000	$14,954,000
Recognized royalty revenue									6,000,000	7,042,000	7,023,000
Roche License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty payments percentage of reported net sales												16.00%
Percentage deduction from royalty payments												50.00%
Percentage distribution charge deducted from net sales												5.50%
Royalty payments percentage of reported adjusted net sales												16.00%
Recognized royalty revenue									6,000,000	7,000,000	7,000,000
Roche License Agreement expected expiration year									2021
Mitsubishi Tanabe Pharma Corporation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront development payment to the company													9,000,000	3,000,000
Funding of development costs													800,000	1,500,000
Number of units for accounting									2
Mitsubishi Tanabe Pharma Corporation [Member] | Collaborative Arrangement One [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized under the first total										2,000,000
Mitsubishi Tanabe Pharma Corporation [Member] | Collaborative Arrangement Two [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized under the first total										$4,100,000

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)	12 Months Ended			1 Months Ended	3 Months Ended
Share data in Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Apr. 30, 2013	Jun. 30, 2013
				Milestone
Operating Leases Of Lessee Future Minimum Payment Term Disclosure [Line Items]
Lease expiry period	2024
Rental expense	$2,100,000	$1,600,000	$1,000,000
Acquired in-process research and development		2,500,000	394,000
Purchase of in-process research and development		2,500,000	344,000
Other License Agreement [Member]
Operating Leases Of Lessee Future Minimum Payment Term Disclosure [Line Items]
Agreements expenses description	Less than $0.1 million	Less than $0.1 million	Less than $0.1 million
Expenses incurred under license agreement	100,000	100,000	100,000
Potential milestone payments under license agreement	100,000
University of Georgia Research Foundation [Member]
Operating Leases Of Lessee Future Minimum Payment Term Disclosure [Line Items]
Amendment agreement date	5-Apr-07
Shares issued in consideration	9
Payments under license agreement	0	0	0
Shire Human Genetic Therapies Inc. and Affiliates [Member]
Operating Leases Of Lessee Future Minimum Payment Term Disclosure [Line Items]
Acquired in-process research and development				2,500,000
Purchase of in-process research and development					$2,500,000
Number of sales based milestones obligation				2
Other Licensing Agreements [Member]
Operating Leases Of Lessee Future Minimum Payment Term Disclosure [Line Items]
Period of potential milestone payments under license agreement	4 years

Commitments_and_Contingencies_2

Commitments and Contingencies - Minimum Future Rentals Under Non-Cancelable Leases (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]
2015, Operating Leases	$2,160
2016, Operating Leases	2,222
2017, Operating Leases	2,187
2018, Operating Leases	2,187
2019, Operating Leases	2,190
2020 and beyond, Operating Leases	49
Total minimum lease payments, Operating Leases	10,995
2015, Capital Leases	439
2016, Capital Leases	448
2017, Capital Leases	457
2018, Capital Leases	466
2019, Capital Leases	475
2020 and beyond, Capital Leases	2,213
Total minimum lease payments, Capital Leases	4,498
Less amount representing interest	-619
Present value of obligations under capital leases	$3,879

Commitments_and_Contingencies_3

Commitments and Contingencies - Minimum Future Rentals Under Non-Cancelable Leases (Parenthetical) (Detail) (USD $)	Dec. 31, 2014
Recorded total leasehold improvements	$4,100,000
Current portion of capital lease obligation	439,000
Bogart, GA [Member]
Current portion of capital lease obligation	$400,000

Quarterly_Financial_Data_Unaud2

Quarterly Financial Data (Unaudited) - Summary of Quarterly Consolidated Statement of Operations Data (Detail) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenue	$1,237	$1,326	$2,343	$1,586	$3,474	$1,369	$3,413	$5,118	$6,492	$13,374	$14,954
Loss from operations	-57,306	-48,038	-50,313	-36,476	-30,944	-28,196	-22,190	-14,573	-192,133	-95,903	-43,021
Net loss	($57,665)	($48,319)	($50,240)	($36,424)	($30,736)	($28,123)	($22,107)	($14,484)	($192,648)	($95,450)	($42,949)
Basic and diluted net loss per share	($1.73)	($1.46)	($1.52)	($1.16)	($1)	($1.02)	($0.81)	($0.54)	($5.89)	($3.40)	($1.90)
Weighted average shares used in basic and diluted per share computations	33,260	33,173	33,057	31,338	30,751	27,491	27,280	26,826	32,719	28,087	22,579

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (Subsequent Event [Member], USD $)	0 Months Ended
In Millions, except Per Share data, unless otherwise specified	Jan. 06, 2015	Jan. 06, 2015
Subsequent Event [Member]
Subsequent Event [Line Items]
Underwritten public offering	$325	$325
Underwritten public offering common stock shares	3.5
Underwritten public offering common stock shares price	$94.19	$94.19
Underwritten public offering net proceeds received	$308.70