Synageva BioPharma 10-K 3 Mar 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Feb. 21, 2014	Jun. 28, 2013
Document And Entity Information [Abstract]	'	'	'
Document Type	'10-K	'	'
Amendment Flag	'false	'	'
Document Period End Date	31-Dec-13	'	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'
Entity Registrant Name	'SYNAGEVA BIOPHARMA CORP	'	'
Entity Central Index Key	'0000911326	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'Yes	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Voluntary Filers	'No	'	'
Entity Filer Category	'Large Accelerated Filer	'	'
Entity Common Stock, Shares Outstanding	'	30,929,969	'
Entity Public Float	'	'	$719.60

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$62,137	$23,883
Short-term investments	346,596	195,070
Accounts receivable	1,373	2,599
Prepaid expenses and other current assets	6,617	3,555
Total current assets	416,723	225,107
Property and equipment, net	17,213	4,012
Developed technology, net	3,491	5,564
Goodwill	8,535	8,535
Other assets	1,987	38
Total assets	447,949	243,256
Current liabilities:	'	'
Accounts payable	2,427	2,576
Accrued expenses	11,261	5,112
Deferred revenue	232	5,391
Total current liabilities	13,920	13,079
Other long term liabilities	3,828	'
Total liabilities	17,748	13,079
Commitments and contingencies (Note 12)	'	'
Stockholders' equity:	'	'
Common stock, par value $0.001; 60,000 shares authorized at December 31, 2013 and 2012, respectively; 30,768 and 24,467 shares issued and outstanding at December 31, 2013 and 2012, respectively	31	24
Additional paid-in capital	684,468	388,936
Accumulated other comprehensive (loss) income	-59	6
Accumulated deficit	-254,239	-158,789
Total stockholders' equity	430,201	230,177
Total liabilities and stockholders' equity	$447,949	$243,256

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, except Per Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	60,000	60,000
Common stock, shares issued	30,768	24,467
Common stock, shares outstanding	30,768	24,467

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues:	'	'	'
Royalty revenue	$7,042	$7,023	$1,083
Collaboration and license revenue	6,332	7,875	640
Other revenue	'	56	376
Total revenue	13,374	14,954	2,099
Costs and expenses:	'	'	'
Research and development	79,644	37,347	17,346
Selling, general and administrative	27,560	17,396	9,268
Amortization of developed technology	2,073	3,232	504
Total costs and expenses	109,277	57,975	27,118
Loss from operations	-95,903	-43,021	-25,019
Other income (expense), net	159	'	-259
Interest income (expense), net	342	72	-28
Loss before provision for income taxes	-95,402	-42,949	-25,306
Provision for income taxes	48	'	'
Net loss	($95,450)	($42,949)	($25,306)
Basic and diluted net loss per share	($3.40)	($1.90)	($8.58)
Weighted average shares used in basic and diluted per share computations	28,087	22,579	2,950

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Loss (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement Of Income And Comprehensive Income [Abstract]	'	'	'
Net loss	($95,450)	($42,949)	($25,306)
Other comprehensive loss:	'	'	'
Fair market value adjustments of available for sale securities	-37	15	'
Foreign currency translation adjustments	-28	-5	-4
Net current period other comprehensive loss	-65	10	-4
Comprehensive loss	($95,515)	($42,939)	($25,310)

Statements_of_Changes_in_Conve

Statements of Changes in Convertible Preferred Stock and Stockholders Equity (Deficit) (USD $)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Total Convertible Preferred Stock [Member]
In Thousands
Beginning Balance at Dec. 31, 2010	($80,178)	$0	$10,356	($90,534)	'	$95,581
Beginning Balance, shares at Dec. 31, 2010	'	61	'	'	'	25,997
Conversion of notes payable to preferred stock	'	'	'	'	'	12,500
Conversion of notes payable to preferred stock, shares	'	'	'	'	'	5,000
Exchange of preferred stock for common stock in connection with the Reverse Merger	108,080	13	108,067	'	'	-108,081
Exchange of preferred stock for common stock in connection with the Reverse Merger, shares	'	12,789	'	'	'	-30,997
Acquisition of Trimeris	69,865	5	69,860	'	'	'
Acquisition of Trimeris, shares	'	4,480	'	'	'	'
Issuance of common stock to underwriter	500	0	500	'	'	'
Issuance of common stock to underwriter, shares	'	33	'	'	'	'
Conversion of preferred stock warrants to common stock warrants	271	'	271	'	'	'
Exercise of common stock warrants	'	0	0	'	'	'
Exercise of common stock warrants, shares	'	10	'	'	'	'
Exercise of stock options	187	0	187	'	'	'
Exercise of stock options, shares	209	209	'	'	'	'
Stock-based compensation expense	633	'	633	'	'	'
Cumulative translation adjustment	-4	'	'	'	-4	'
Net loss	-25,306	'	'	-25,306	'	'
Ending Balance at Dec. 31, 2011	74,048	18	189,874	-115,840	-4	'
Ending 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	1	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	'	'	'	'
Issuance of common stock- ESPP	190	'	190	'	'	'
Issuance of common stock- ESPP ,shares	'	5	'	'	'	'
Exercise of stock options	4,969	1	4,968	'	'	'
Exercise of stock options, shares	660	660	'	'	'	'
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	'	'	'	'

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities	'	'	'
Net loss	($95,450)	($42,949)	($25,306)
Adjustments:	'	'	'
Depreciation and amortization	5,566	4,272	1,034
Stock compensation expense	9,187	4,971	633
Amortization of premium on investments	2,486	310	'
Acquired in-process research and development	2,500	344	'
Revaluation of preferred stock warrants	'	'	259
Changes in assets and liabilities, net of acquisition:	'	'	'
Accounts receivable	1,226	-388	1,586
Prepaid expenses, other current assets, and other assets	-3,076	-1,324	-464
Accounts payable	-149	1,069	1,079
Accrued expenses	7,294	109	1,850
Deferred revenue	-5,159	2,651	2,740
Deferred rent	573	'	'
Net cash used in operating activities	-75,002	-30,935	-16,589
Cash flows from investing activities	'	'	'
Purchase of available for sale investments	-425,999	-195,365	'
Proceeds from sales and maturities of available for sale investments	271,950	'	'
Capital expenditures	-14,621	-3,746	-683
Purchase of in-process research and development and other assets	-2,500	-394	'
Change in restricted cash	-1,935	'	'
Cash received from merger	'	'	50,107
Net cash (used in) provided by investing activities	-173,105	-199,505	49,424
Cash flows from financing activities	'	'	'
Proceeds from issuance of common stock, net of issuance costs	281,193	192,736	'
Proceeds from exercise of stock options	5,159	1,361	186
Proceeds from issuance of convertible notes	'	'	12,500
Net cash provided by financing activities	286,352	194,097	12,686
Effect of exchange rate on cash	9	-6	-4
Net increase (decrease) in cash and equivalents	38,254	-36,349	45,517
Cash and equivalents at the beginning of period	23,883	60,232	14,715
Cash and equivalents at the end of period	$62,137	$23,883	$60,232

Nature_of_the_Business

Nature of the Business	12 Months Ended
	Dec. 31, 2013
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’s most advanced pipeline programs are enzyme replacement therapies for lysosomal storage diseases (“LSDs”). The Company’s lead program, sebelipase alfa, is in global Phase 3 clinical investigation for the treatment of infants, children and adults with lysosomal acid lipase (“LAL”) Deficiency, a rare but devastating disease that causes significant morbidity and mortality. In addition to sebelipase alfa, the Company has multiple other ongoing research programs at different stages of preclinical development, including SBC-103, another enzyme replacement therapy for an LSD known as mucopolysaccharidosis type IIIB (“MPS IIIB”) or Sanfilippo B. The Company’s pipeline programs target rare diseases that are characterized by significant morbidity and mortality and are selected based on scientific rationale, high unmet medical need, the potential to impact disease course and strategic alignment with our corporate focus. The Company has not yet received approval to market or commercialize sebelipase alfa or any other products.
	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, 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, technological and medical risks and management of growth.
	The Company has incurred losses since inception and at December 31, 2013, had an accumulated deficit of $254.2 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, including some or all of its drug candidates.
	Through December 31, 2013, the Company has funded its operations primarily from proceeds of the sale of stock, royalty income and collaboration agreements. On September 30, 2013, the Company announced the closing of a $179.1 million underwritten public offering of approximately 3.2 million shares of common stock at a price per share of $56.63. The Company received net proceeds of approximately $170.1 million from this offering. In addition, on January 9, 2013, the Company announced the closing of a $117.5 million underwritten public offering of approximately 2.5 million shares of common stock at a price per share of $47.53. The Company received net proceeds of approximately $111.1 million from this offering. In addition to these financings, the Company received net proceeds of $192.7 million from two public equity offerings in fiscal 2012.
	The Company intends to use its cash, cash equivalents and investments for general corporate purposes, which may include expanding our infrastructure to benefit sebelipase alfa and our platform, supporting our clinical studies, supporting the advancement of SBC-103, accelerating our early-stage programs, leveraging our platform technology to initiate multiple new pipeline programs and acquiring technologies or businesses that are complementary to our current technologies and business focus. The Company expects that it will have sufficient cash and cash equivalents to sustain operations to at least the second half of 2015.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2013
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.
	See Note 5 for additional discussion of the Reverse Merger and the conversion ratio.
	Cash and Cash Equivalents
	The Company considers all highly liquid investments with a remaining maturity at the date of purchase of less than three months to be cash equivalents. At December 31, 2013 and 2012, 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, 2013 and December 31, 2012. 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, 2013:
	U.S. Treasury securities		$	346,618		$	—		$	(22	)	$	346,596
	Total		$	346,618		$	—		$	(22	)	$	346,596
	Balance at December 31, 2012:
	U.S. Treasury securities		$	195,055		$	15		$	—		$	195,070
	Total		$	195,055		$	15		$	—		$	195,070
	The Company completed an evaluation of its investments and determined that it did not have any other-than-temporary impairments as of December 31, 2013 or 2012. 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 Price			Significant			Significant
			2013			in Active			Other			Unobservable
						Markets			Observable			Inputs
						(Level 1)			Inputs			(Level 3)
									(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		$	—
	Items classified as Level 2 within the valuation hierarchy consist of institutional money market funds, and U.S. government-related debt securities. 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, 2012:
			December 31,			Quoted Price			Significant			Significant
			2012			in Active			Other			Unobservable
						Markets			Observable			Inputs
						(Level 1)			Inputs			(Level 3)
									(Level 2)
	Assets
	Cash equivalents
	Money market fund		$	10,387		$	10,387		$	—		$	—
	US treasury securities			10,011			10,011			—		$	—
	Marketable securities
	US treasury securities		$	195,070		$	195,070		$	—		$	—
	Total		$	215,468		$	215,468		$	—		$	—
	Impairment of Other Long-Lived Tangible and Intangible 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.
	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 6 “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, 2013. See Note 6, “Goodwill and Intangible Assets, Net,” for additional information.
	Revenue Recognition
	The Company’s business strategy includes 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”). In January 2011, the Company adopted Accounting Standards Update (“ASU”) No. 2009-13, “Multiple Deliverable Revenue Arrangements” for contracts entered into or materially modified after that date. ASU 2009-13 updates the previous multiple-element revenue arrangements guidance. The revised guidance primarily provides three significant changes: 1) it eliminates the need for objective and reliable evidence of the fair value of the undelivered element in order for a delivered item to be treated as a separate unit of accounting; 2) it eliminates the residual method to allocate the arrangement consideration; and 3) it modifies the fair value requirements of EITF Issue 00-21 by providing best estimate of selling price, or BESP, in addition to vendor specific objective evidence and vendor objective evidence, or VSOE, for determining the selling price of a deliverable. In addition, the guidance also expands the disclosure requirements for revenue recognition. 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.
For multiple element arrangements, including collaboration and license agreements, entered into prior to January 1, 2011, guidance required that the fair value of the undelivered item be the price of the item either sold in a separate transaction between unrelated third parties or the price charged for each item when the item is sold separately by the vendor. This was difficult to determine when the service or product was not individually sold because of its unique features. Under this guidance, if the fair value of all of the undelivered elements in the arrangement was not determinable, then revenue was deferred until all of the items were delivered or fair value was determined.
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 11, “License Agreements and Collaborations,” for additional information on specific arrangements. Collaboration and license revenue totaled approximately $6.3 million, $7.9 million and $0.6 million for the years ended December 31, 2013, 2012 and 2011, respectively.
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 $7.0 million, $7.0 million and $1.1 million for the year ended December 31, 2013, 2012 and the approximate two month post-merger period ending December 31, 2011, 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 FASB Codification Topic 605-45, Revenue Recognition, Principal Agent Considerations, the amounts are determinable and collection of the related receivable is reasonably assured.
Grant Revenue
The Company recognizes revenues from grants in the period in which the Company has incurred the expenditures in compliance with the specific restrictions of the grant.
Revenue from grants was recognized in the period in which the related expenditures were incurred and totaled approximately $0.1 million and 0.4 million for the years ended December 31, 2012 and 2011, respectively, and are reflected as other revenue in the statements of operations.
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,
		2013			2012			2011
Numerator:
Net loss		$	(95,450	)	$	(42,949	)	$	(25,306	)
Denominator
Weighted average common shares(1)
Denominator for basic calculation			28,087			22,579			2,950
Denominator for diluted calculation			28,087			22,579			2,950
Net loss per share:(1)
Basic		$	(3.40	)	$	(1.90	)	$	(8.58	)
Diluted		$	(3.40	)	$	(1.90	)	$	(8.58	)
	-1	Per share computations for fiscal 2011 are based on (i) Private Synageva’s historic common stock balances (excluding preferred stock) up to the Reverse Merger date and (ii) post-Reverse Merger common stock from the Reverse Merger date to year end.
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,
		2013			2012			2011
Options to purchase common stock			2,710			2,529			2,371
Recently Issued and Proposed Accounting Pronouncements
In February 2013, the Financial Accounting Standards Board (“FASB”) issued an accounting standard update related to Comprehensive Income: Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income. The revised standard requires companies to present information about reclassification adjustments from accumulated other comprehensive income in their annual financial statements in a single note or on the face of the financial statements. The Company adopted this standard in the first quarter of 2013 and presented this information below under the heading, Accumulated Other Comprehensive Income (Loss) to these consolidated financial statements. The adoption of this standard did not have an impact on our financial position or results of operations.
In July 2013, the FASB issued an accounting standards update clarifying the presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. The updated guidance requires the netting of unrecognized tax benefits against a deferred tax asset for a loss or other carryforward when settlement of the liability for an unrecognized tax benefit in this manner is available. The update is effective prospectively for reporting periods beginning after December 15, 2013, and early adoption and retrospective adoption are permitted. The adoption of this guidance is not currently expected to have a material impact on the Company’s consolidated financial statements or disclosures.
Accumulated Other Comprehensive Loss
The following table summarizes the changes in accumulated other comprehensive income (loss), net of tax by component:
		Unrealized			Translation			Total
		Gains on			Adjustments
		Available
		for Sale
		Securities
Balance, as of December 31, 2012			15			(9	)		6
Other comprehensive loss before reclassifications			(37	)		(28	)		(65	)
Amounts reclassified from accumulated other comprehensive loss			—			—			—
Net current period other comprehensive loss			(37	)		(28	)		(65	)
Balance, as of December 31, 2013			(22	)		(37	)		(59	)

Property_and_Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2013
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
	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 construction of the shell buildings is being provided by the landlord and is expected to be completed in mid-2014. In conjunction with the construction, the Company will be outfitting the shell buildings to its specifications, at an estimated cost of approximately $11 million.
	The landlord construction and tenant improvements will be in accordance with the Company’s plans and include substantial outfitting of the building. The scope of the planned tenant improvements do not qualify as “normal tenant improvements” under the lease accounting guidance. Accordingly, for accounting purposes, the Company is the deemed owner of the buildings during the construction period. As construction progresses, the Company records 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. Upon completion of the buildings, the Company will determine if the assets and corresponding financing obligation should continue to be carried on its balance sheet under the accounting guidance. Based on the current terms of the lease, the Company expects to continue to be the deemed owner of the buildings upon completion of the construction period. As of December 31, 2013, the Company has recorded construction in process and a facility lease obligation of $1.7 million.
	Lexington, MA Headquarters and Lab Buildout
	In January 2013, the Company entered into a lease agreement to accommodate the Company’s continue growth and to relocate its corporate headquarters in Lexington, Massachusetts. The Company began occupying the facility in the second quarter of 2013. The Company spend approximately $5.0 million to buildout the lab facilities, $1.2 million of which was in the form of a landlord funded tenant allowance. The Company has established a long-term liability for the landlord funded tenant allowance that is being amortized ratably over the life of the lease.
	The following summarizes our property and equipment balances as of December 31, 2013 and 2012:
			December 31,
			2013			2012
	Laboratory equipment		$	6,228		$	3,478
	Leasehold improvements			13,923			2,748
	Computer, software and other			2,048			1,115
	Construction in process			1,713			—
				23,912			7,341
	Less: Accumulated depreciation and amortization			(6,699	)		(3,329	)
			$	17,213		$	4,012
	Depreciation expense was $3.5 million, $1.0 million and $0.5 million for fiscal years 2013, 2012, and 2011, respectively.

Supplemental_Balance_Sheet_Dat

Supplemental Balance Sheet Data	12 Months Ended
	Dec. 31, 2013
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,
			2013		2012
	Prepaid clinical, manufacturing, and scientific costs		$	3,960	$	1,598
	Interest receivable			859		603
	Prepaid insurance			958		896
	Other			840		458
			$	6,617	$	3,555
	Other non-current assets consist of the following:
			December 31,
			2013		2012
	Restricted cash		$	1,935	$	—
	Other			52		38
			$	1,987	$	38
	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,
			2013		2012
	Accrued compensation and benefits		$	3,244	$	1,862
	Clinical, manufacturing and scientific costs			6,587		1,978
	Professional fees			568		685
	Other			862		587
			$	11,261	$	5,112

Reverse_Merger

Reverse Merger	12 Months Ended
	Dec. 31, 2013
Business Combinations [Abstract]	'
Reverse Merger	'
	5	Reverse Merger
	On November 2, 2011, the Company completed the Reverse Merger, which was accounted for as a reverse acquisition under the acquisition method of accounting, with Private Synageva treated as the accounting acquiror and Trimeris treated as the “acquired” company for financial reporting purposes because, after the Merger, former stockholders of Private Synageva held a majority of the voting interest of the combined company. In addition, the former board of directors of Private Synageva possessed majority control of the board of directors of the combined company. Members of the management of Private Synageva are responsible for the management of the combined company and the majority of the combined company’s activities are related to Synageva’s current business. As such, the financial statements of Private Synageva are treated as the historical financial statements of the combined company, with the results of Trimeris being included from November 2, 2011.
	Reverse Stock Split
	On November 2, 2011, as contemplated by the Merger Agreement and as approved by Trimeris’ stockholders, Trimeris filed a Certificate of Amendment to its Fifth Amended and Restated Certificate of Incorporation with the Secretary of State of the State of Delaware to effect a reverse stock split of Trimeris common stock at a ratio of 1:5 (the “Reverse Stock Split”). As a result of the Reverse Stock Split, each five shares of Trimeris common stock issued and outstanding immediately prior to the Reverse Stock Split were automatically combined into and became one share of Trimeris common stock. No fractional shares of Trimeris common stock were issued as a result of the Reverse Stock Split and any Trimeris stockholder who otherwise would have been entitled to receive fractional shares received cash in an amount, without interest, determined by multiplying such fraction of a share by $15.35, the closing price of a share of Trimeris common stock on the Nasdaq Global Market on November 2, 2011, after giving effect to the Reverse Stock Split. Also, as a result of the Reverse Stock Split, the per share exercise price of, and the number of shares of common stock underlying, Company stock options, warrants and other derivative securities outstanding immediately prior to the Reverse Stock Split were automatically proportionally adjusted based on the one-for-five split ratio in accordance with the terms of such options, warrants or other derivative securities, as the case may be. The Reverse Stock Split did not alter the par value of the Trimeris common stock or modify any voting rights or other terms of the common stock. Following the Reverse Stock Split, but prior to the Reverse Merger, there were 4.5 million shares of Trimeris stock outstanding.
	Exchange Ratio
	Based on the outstanding shares of Private Synageva’s capital stock on November 2, 2011, each share of Private Synageva’s preferred stock and common stock was exchanged for approximately 0.413 shares of Trimeris common stock (the “Exchange Ratio”). As part of the Reverse Merger, Private Synageva’s convertible notes payable were converted into D-2 Preferred Stock, prior to the conversion of all of Private Synageva’s preferred stock and common stock into shares of the combined company. The conversion of Private Synageva’s preferred stock and common stock resulted in 13.0 million shares in the combined company.
	In addition, (i) all outstanding options to purchase shares of Private Synageva common stock were assumed by Trimeris and converted into options to purchase shares of Trimeris common stock, in each case appropriately adjusted based on the Exchange Ratio; and (ii) all outstanding warrants to purchase shares of the capital stock of Private Synageva were assumed by Trimeris and converted into warrants to purchase shares of Trimeris common stock, in each case appropriately adjusted based on the Exchange Ratio. Immediately after the Reverse Merger, former stockholders of Private Synageva held approximately 75% of the combined company, calculated on a fully-diluted basis, and former stockholders of Trimeris held approximately 25% of the combined company, calculated on a fully-diluted basis, in each case excluding those shares of Trimeris held by the former Private Synageva stockholders immediately prior to the time of the Reverse Merger. After giving effect to the Reverse Stock Split and the Reverse Merger, the combined company had approximately 17.5 million shares of common stock outstanding.
	Merger Purchase Price
	The consolidated financial statements reflect the merger of Synageva with Trimeris as a reverse merger wherein Synageva is deemed to be the acquiring entity from an accounting perspective. Under the acquisition method of accounting, Trimeris’ 4.5 million of outstanding shares of common stock (following the stock split but prior to the Merger) were valued using the closing price on the Nasdaq Global Market of $15.35 per share on November 2, 2011. Further, as a result of the Reverse Merger, options to purchase an aggregate of 0.4 million shares of Trimeris common stock that were held by officers and directors of Trimeris immediately vested (see Note 9). The fair values of the Trimeris outstanding stock options were determined using the Black-Scholes option pricing model with the following assumptions: stock price of $15.35; volatility of 51%; risk-free interest rate of 1.02%; and a weighted average expected life of 2.8 years. In addition, Synageva incurred approximately $1.1 million of transaction costs related to the Reverse Merger. These costs were expensed as incurred, and classified as general and administrative expense.
	The purchase price, based on the stock price as of the Reverse Merger date, was as follows:
	Fair value of Trimeris shares outstanding		$	68,767
	Fair value of vested Trimeris stock options			1,102
	Purchase price		$	69,869
	Reverse Merger Purchase Price Allocation
	The fair value of acquired assets and liabilities were as follows (in thousands):
	Cash and cash equivalents		$	50,107
	Accounts receivable, taxes refundable and other current assets			4,437
	Developed technology—FUZEON			9,300
	Goodwill(1)			8,535
	Assumed liabilities			(2,510	)
	Total		$	69,869
		-1	The goodwill resulting from the Reverse Merger is not deductible for tax purposes.
	Pro Forma Financial Information
	The following table presents selected unaudited financial information, as if the Reverse Merger with Trimeris had occurred on January 1, 2010 (in thousands, except per share data).
			Year Ended
			2011
			(Unaudited)
	Pro forma net revenue(1)		$	10,035
	Pro forma net (loss) income			(22,337	)
	Pro forma net (loss) income per common share—basic		$	(4.82	)
	Pro forma net (loss) income per common share—diluted		$	(4.82	)
		-1	Fiscal 2010 revenue includes $18.7 million of revenue resulting from entering into the Deferred Marketing Expenses Agreement with Roche, which relieved the obligation to repay certain deferred marketing expenses.
	Fiscal 2011 pro forma net loss incorporates the elimination of $5.2 million of acquisition-related costs, which have been reflected in the 2010 pro forma net loss. Both 2011 and 2010 pro forma net loss includes $3.2 million of estimated amortization expense related to acquired developed technology.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets, Net	12 Months Ended
	Dec. 31, 2013
Goodwill And Intangible Assets Disclosure [Abstract]	'
Goodwill and Intangible Assets, Net	'
	6	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, 2013, and notes that its goodwill is not impaired as of December 31, 2013.
	Intangible assets, net of accumulated amortization is as follows (in thousands):
					As of December 31, 2013
			Initial		Cost		Accumulated			Net
			Estimated Life				Amortization
	Developed Technology			10 years	$	9,300	$	(5,809	)	$	3,491
	The developed technology asset represents the present value of the estimated future FUZEON royalty stream (Note 11). Amortization expense totaled $2.1 million, $3.2 million and $0.5 million for fiscal 2013, 2012 and 2011, 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)
	2014		$	1,218
	2015			847
	2016			555
	2017			361
	2018 and beyond			510

Convertible_Notes_and_Converti

Convertible Notes and Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2013
Text Block [Abstract]	'
Convertible Notes and Convertible Preferred Stock	'
	7	Convertible Notes and Convertible Preferred Stock
	Convertible Preferred Stock
	As of December 31, 2010, of the 28,000 authorized shares of preferred stock, 246 shares were designated as Series A-2 convertible preferred stock (“Series A-2 preferred stock”), 4,169 shares were designated as Series B-2 convertible preferred stock (“Series B-2 preferred stock”), 3,659 shares were designated as Series C-2 convertible preferred stock (“Series C-2 preferred stock”), and 18,000 shares were designated as Series D-2 preferred stock. These shares converted to common stock of the combined company as part of the Reverse Merger at a ratio of approximately 0.413 for every share of previously issued stock. There were no shares of authorized preferred stock outstanding at December 31, 2013, 2012 or 2011.
	2011 Convertible Notes
	In March 2011, the Company issued Convertible Notes (the “2011 Convertible Notes”) for proceeds of $12.5 million as the first tranche of a potential $25 million convertible note offering. The 2011 Convertible Notes were convertible into shares of Series D-2 preferred stock at the conversion price then applicable to the Series D-2 preferred stock or into a future series of Preferred Stock at its then applicable conversion price issued in conjunction with the next Qualified Offering (as defined in the 2011 Notes purchase agreement), at the election of the holders. The 2011 Convertible Notes had no stated interest rate. On November 2, 2011 as part of the completion of the merger with Trimeris, the 2011 Convertible Notes were converted into D-2 Preferred Stock, prior to the conversion of all Private Synageva preferred and common shares outstanding into shares of the combined entity.

Share_Based_Payments

Share Based Payments	12 Months Ended
	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Share Based Payments	'
	8	Share Based Payments
	The Company’s stock-based compensation plans include the 1996 Stock Option Plan and the 2005 Stock Plan, as well as options outstanding under Trimeris, Inc.’s 1993 Plan and 2007 Stock Incentive Plan. As part of the Reverse Merger, options outstanding under Trimeris’s previous option plans were adjusted by the conversion ratio, and remain in existence as options in the combined entity. The Board of Directors has the authority to determine to whom options will be granted, the number of shares, the term, and the exercise price.
	At the Company’s annual meeting of stockholders held June 6, 2013, stockholders approved amendments to the 2005 Stock Plan to increase the number of shares of common stock available for issuance by 1.5 million shares, increasing the maximum number of shares that may be issued under the 2005 Stock Plan to approximately 4.9 million shares. Shares subject to outstanding awards under the 2005 Stock Plan totaled 2.5 million as of December 31, 2013. At December 31, 2013, there were 1.1 million shares remaining available for grant under the 2005 Stock Plan.
	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%. 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. Approximately five thousand shares were issued with the June 30, 2013 purchase. Approximately six thousand shares were issued in connection with the December 31, 2013 purchase in early 2014, and therefore, were not considered in our outstanding common stock balance as of December 31, 2013.
	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: 1) Historical experience and peer group (including industry, size, life cycle and financial leverage), and 2) Implied volatility from publicly traded options with the longest available contractual terms. The Company’s peer group includes companies that are similar to us in terms of size, stage of life cycle and financial leverage. The risk-free interest rate is based on the rate of 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,
			2013			2012			2011
	Expected dividend yield			None			None			None
	Weighted average volatility in stock price			58	%		50	%		51	%
	Weighted average risk-free interest rate			1.39	%		0.88	%		1.51	%
	Expected life of stock awards-years			6 years			6 years			6 years
	The assumptions used to estimate the per share fair value of stock purchase rights granted under the ESPP were as follows for 2013, the first year of our ESPP:
			Year Ended
			December  31,
			2013
	Expected volatility		38.5-49.6%
	Dividend yield		0.00%
	Expected life		6 months
	Risk-free interest rate		0.09-.12%
	A summary of stock option activity under all equity plans for the year ended December 31, 2013, 2012, and 2011 is as follows:
			Number of			Weighted
			Shares			Average
						Exercise Price
	Outstanding at December 31, 2010			1,244		$	1.27
	Options granted			1,029			13.39
	Options assumed through merger with Trimeris			373			57.23
	Options exercised			(209	)		0.89
	Options canceled or expired			(66	)		1.41
	Outstanding at December 31, 2011			2,371		$	15.34
	Options granted			820			43.9
	Options exercised			(519	)		2.62
	Options canceled or expired			(143	)		53.83
	Outstanding at December 31, 2012			2,529		$	25.06
	Options granted			1,119			45.31
	Options exercised			(660	)		7.52
	Options canceled or expired			(278	)		60.8
	Outstanding at December 31, 2013			2,710		$	34.05
	Exercisable at December 31, 2013			1,000		$	26.39
	Exercisable and expected to vest at December 31, 2013			2,521		$	33.71
	The weighted average grant date fair value of options granted in 2013, 2012 and 2011 was $23.41, $20.38 and $8.11, respectively. The total intrinsic value of stock options exercised during the years ended December 31, 2013, 2012 and 2011 was $28.3 million, $21.2 million and $1.0 million, respectively.
	Options outstanding and currently exercisable at December 31, 2013, 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			102			5.6		$	0.94			102	$	0.94
	$1.10-$1.70			200			7.1			1.66			76		1.61
	$3.52-$8.73			160			6.2			6.08			116		5.1
	$10.10-$20.60			34			5.6			13.94			34		13.94
	$23.00-$45.50			1,701			8.5			35.69			536		31.73
	$45.51-$69.50			509			8.1			57.56			132		58.56
	$94.80-$194.00			4			0.1			94.8			4		94.8
				2,710			8		$	34.05			1,000	$	26.39
	As of December 31, 2013, the unamortized compensation expense related to outstanding unvested options approximated $31.5 million and is expected to be recognized over a weighted average period of 2.7 years.
	The aggregate intrinsic value of shares outstanding and shares exercisable at December 31, 2013 is approximately $83.3 million and $38.5 million, respectively, which represents the total intrinsic value (the excess of the fair value of the Company’s stock on December 31, 2013 over the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on December 31, 2013.
	The Company recognized stock-based compensation expense on all stock option awards as follows:
			Year Ended December 31,
			2013			2012			2011
	Research and development		$	3,586		$	1,432		$	231
Selling, general and administrative			5,601			3,539			402
		$	9,187		$	4,971		$	633

Defined_Contribution_Plan

Defined Contribution Plan	12 Months Ended
	Dec. 31, 2013
Postemployment Benefits [Abstract]	'
Defined Contribution Plan	'
	9	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, 2013, 2012 and 2011, the Company recognized expense for 401(k) matching contributions of $0.5 million, $0.2 million and $0.2 million, respectively.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2013
Income Tax Disclosure [Abstract]	'
Income Taxes	'
	10	Income Taxes
	For financial reporting purposes, loss before income taxes includes the following components for the year ended December 31:
			Year Ended December 31,
			2013			2012			2011
	U.S. pretax loss		$	(95,588	)	$	(43,032	)	$	(25,402	)
	Non-U.S. pretax income			186			83			96
	Loss before provision for income taxes		$	(95,402	)	$	(42,949	)	$	(25,306	)
	The Company has not recorded a benefit for income taxes related to its U.S. operating losses for the years ended December 31, 2013, 2012 or 2011. The Company is in a full valuation allowance for our U.S. operations as it is more-likely-than-not that we will not utilize our net deferred assets. In 2013, the Company recorded a minimal current income tax provision related to certain international subsidiaries that are profitable on a stand-alone basis based on intercompany service arrangements.
	The Company’s effective tax rate differs from that based on the federal statutory rate due to the following:
			Years Ended December 31,
			2013			2012			2011
	Federal tax at statutory rate		$	(32,453	)	$	(14,603	)	$	(8,571	)
	State income taxes			(3,580	)		(1,149	)		(1,278	)
	State rate changes			215			2,161			(1,443	)
	Federal and state credits			(21,186	)		(15,784	)		(1,611	)
	Trimeris net operating losses			—			—			(9,481	)
	Nondeductible 162(m) compensation			2,780			—			—
	Expiration of state NOLs			46			11,129			337
	Stock-based compensation			564			335			(26	)
	Valuation allowance			53,155			17,887			22,081
	Other			507			24			(8	)
	Provision for income taxes		$	48		$	—		$	—
	Significant components of the Company’s net deferred tax asset as December 31, 2013 and 2012 are as follows:
			2013			2012
	Deferred tax assets:
	Net operating losses		$	42,962		$	37,451
	Capitalized research and development			23,822			10,286
	Tax credit carryforwards			57,155			25,693
	Deferred revenue			87			2,056
	Accrued expenses			210			142
	Depreciation and amortization			1,787			235
	Stock-based compensation			3,411			1,289
	Other			11			10
				129,445			77,162
	Deferred tax liabilities:
	Acquired intangibles			(655	)		(1,527	)
	Valuation allowance			(128,790	)		(75,635	)
	Net deferred tax asset		$	—		$	—
	At December 31, 2013, the Company had federal and state net operating loss carry forwards of $158.1 million and $110.6 million, respectively, which begin to expire in 2018 and 2014, respectively. Approximately $0.9 million of Massachusetts net loss carry forwards expired in 2013. In conjunction with ceasing of Trimeris operations in 2012, approximately $11.1 million of tax effected state net operating loss carryforwards expired (or were forfeited) in the prior year. The Company has federal orphan drug credits and federal and state research tax credit carryforwards of $57.1 million, available to reduce future tax liabilities, which begin expiring in 2018 and 2023, respectively. Included in our December 31, 2012 deferred tax balance were orphan drug credits that were generated in earlier periods, resulting in a net increase in our gross deferred tax asset balance of approximately $4.1 million. Given the corresponding increase in the valuation allowance, this out-of-period adjustment had no impact on the Company’s balance sheet, statement of operations, or statement of cash flows and is considered immaterial to the Company’s prior period financial statements taken as a whole. Approximately $42.3 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 $128.8 million and $75.7 million has been established at December 31, 2013 and 2012, respectively.
	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			2010
	State of Georgia			2010
	State of North Carolina			2010
	Commonwealth of Massachusetts			2010
	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 2010 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 2013 and 2012.
	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, 2013. It is not practicable to estimate the amount of deferred tax liability related to investments in these foreign subsidiaries. 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, 2013 and 2012.
	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. We recognized $0.1 million in 2013, related to the award.

License_Agreements_and_Collabo

License Agreements and Collaborations	12 Months Ended
	Dec. 31, 2013
Organization Consolidation And Presentation Of Financial Statements [Abstract]	'
License Agreements and Collaborations	'
	11	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, and $1.9 million and $6.0 million, respectively for the year ended December 31, 2012. Revenue is 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 $7.0 million, $7.0 million and $1.1 million for the years ended December 31, 2013, 2012 and 2011, 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, 2013
Commitments And Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	12	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, 2013:
	Year Ending December 31,		Operating		Capital
			Leases		Leases
	2014		$	1,490	$	253
	2015			1,501		439
	2016			1,516		448
	2017			1,519		457
	2018			1,527		466
	2019 and beyond			1,579		2,688
	Total minimum lease payments		$	9,132	$	4,751
	Less amount representing interest					(700	)
	Present value of obligations under capital leases (1)				$	4,051
		-1	The Company’s capital lease obligation relates to the construction of a manufacturing facility in Bogart, GA. As of December 31, 2013, the Company has recorded construction in process and a facility lease obligation of $1.7 million. Upon the completion of the landlord construction in 2014, the Company estimates that the present value of the obligation will be approximately $4.1 million. The current portion of capital lease obligation was less than $0.1 million as of December 31, 2013.
	Rental expense for the years ended December 31, 2013, 2012 and 2011 approximated $1.6 million, $1.0 million and $0.7 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 2013, 2012 and 2011.
	Shire Human Genetics Therapies
	In April 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 sebelipase alfa 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 sebelipase alfa 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, 2013, 2012 and 2011. At December 31, 2013, 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, 2013
Quarterly Financial Information Disclosure [Abstract]	'
Quarterly Financial Data (Unaudited)	'
	13	Quarterly Financial Data (Unaudited)
	The following tables present quarterly consolidated statement of operations data for fiscal 2013 and 2012. 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,
			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
			Three Months Ended
			March 31,			June 30,			September 30,			December 31,
			2012			2012			2012			2012
			(unaudited)
	Revenue		$	2,397			2,249		$	5,428		$	4,880
	Loss from operations			(7,355	)		(10,226	)		(10,189	)		(15,251	)
	Net loss			(7,353	)		(10,223	)		(10,182	)		(15,191	)
	Loss per share, basic and diluted		$	(0.35	)	$	(0.48	)	$	(0.43	)	$	(0.62	)
	Weighted average shares outstanding, basic and diluted			20,774			21,284			23,825			24,347

Supplemental_Disclosures_of_Ca

Supplemental Disclosures of Cash Flow Information	12 Months Ended
	Dec. 31, 2013
Supplemental Cash Flow Elements [Abstract]	'
Supplemental Disclosures of Cash Flow Information	'
	14	Supplemental Disclosures of Cash Flow Information
	The following schedule summarizes the Company’s supplemental noncash investing and financing activities that are not presented in the statement of cash flows:
			Years Ended December 31,
			2013		2012		2011
	Supplemental schedule of noncash investing and financing activities
	Capitalization of construction-in-progress related to facility lease obligation (Note 3)		$	1,713		—		—
	Capital expenditures incurred but not yet paid		$	360		—		—
	Related to Reverse Merger:
	Conversion of convertible note into preferred stock			—		—		12,500
	Conversion of preferred stock into common stock			—		—		108,081
	Payments made in common stock to underwriter			—		—		500
	Conversion of preferred stock warrants to common stock warrants			—		—		271
	Fair value of assets acquired in Merger		$	—	$	—	$	72,379
	Fair value of liabilities assumed in Merger			—		—		(2,510	)
	Fair value of net assets acquired in Merger		$	—	$	—	$	69,869

Subsequent_Events

Subsequent Events	12 Months Ended
	Dec. 31, 2013
Subsequent Events [Abstract]	'
Subsequent Events	'
	15	Subsequent Events
	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 anticipates that it will occupy the expanded space in June 2014 upon the completion of landlord building modifications. The initial rent for the additional space will be $22.50 per square foot plus certain operating expenses and taxes. The Company will have the right to occupy the entire additional space upon the completion of the building modifications, but it will pay rent on only 9,524 square feet for the first two months and on 19,048 for the following eight months, before paying rent on the full 29,316 rentable square feet thereafter. The total combined leased space, including the additional space, will consist of 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.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
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.
	See Note 5 for additional discussion of the Reverse Merger and the conversion ratio.
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.
	See Note 5 for additional discussion of the Reverse Merger and the conversion ratio.
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 less than three months to be cash equivalents. At December 31, 2013 and 2012, 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, 2013 and December 31, 2012. 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, 2013:
	U.S. Treasury securities		$	346,618		$	—		$	(22	)	$	346,596
	Total		$	346,618		$	—		$	(22	)	$	346,596
	Balance at December 31, 2012:
	U.S. Treasury securities		$	195,055		$	15		$	—		$	195,070
	Total		$	195,055		$	15		$	—		$	195,070
	The Company completed an evaluation of its investments and determined that it did not have any other-than-temporary impairments as of December 31, 2013 or 2012. 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 Price			Significant			Significant
			2013			in Active			Other			Unobservable
						Markets			Observable			Inputs
						(Level 1)			Inputs			(Level 3)
									(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		$	—
	Items classified as Level 2 within the valuation hierarchy consist of institutional money market funds, and U.S. government-related debt securities. 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, 2012:
			December 31,			Quoted Price			Significant			Significant
			2012			in Active			Other			Unobservable
						Markets			Observable			Inputs
						(Level 1)			Inputs			(Level 3)
									(Level 2)
	Assets
	Cash equivalents
	Money market fund		$	10,387		$	10,387		$	—		$	—
	US treasury securities			10,011			10,011			—		$	—
	Marketable securities
	US treasury securities		$	195,070		$	195,070		$	—		$	—
	Total		$	215,468		$	215,468		$	—		$	—
Impairment of Other Long-Lived Tangible and Intangible Assets	'
	Impairment of Other Long-Lived Tangible and Intangible 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.
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 6 “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, 2013. See Note 6, “Goodwill and Intangible Assets, Net,” for additional information.
Revenue Recognition	'
	Revenue Recognition
	The Company’s business strategy includes 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”). In January 2011, the Company adopted Accounting Standards Update (“ASU”) No. 2009-13, “Multiple Deliverable Revenue Arrangements” for contracts entered into or materially modified after that date. ASU 2009-13 updates the previous multiple-element revenue arrangements guidance. The revised guidance primarily provides three significant changes: 1) it eliminates the need for objective and reliable evidence of the fair value of the undelivered element in order for a delivered item to be treated as a separate unit of accounting; 2) it eliminates the residual method to allocate the arrangement consideration; and 3) it modifies the fair value requirements of EITF Issue 00-21 by providing best estimate of selling price, or BESP, in addition to vendor specific objective evidence and vendor objective evidence, or VSOE, for determining the selling price of a deliverable. In addition, the guidance also expands the disclosure requirements for revenue recognition. 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.
	For multiple element arrangements, including collaboration and license agreements, entered into prior to January 1, 2011, guidance required that the fair value of the undelivered item be the price of the item either sold in a separate transaction between unrelated third parties or the price charged for each item when the item is sold separately by the vendor. This was difficult to determine when the service or product was not individually sold because of its unique features. Under this guidance, if the fair value of all of the undelivered elements in the arrangement was not determinable, then revenue was deferred until all of the items were delivered or fair value was determined.
	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 11, “License Agreements and Collaborations,” for additional information on specific arrangements. Collaboration and license revenue totaled approximately $6.3 million, $7.9 million and $0.6 million for the years ended December 31, 2013, 2012 and 2011, respectively.
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 $7.0 million, $7.0 million and $1.1 million for the year ended December 31, 2013, 2012 and the approximate two month post-merger period ending December 31, 2011, 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 FASB Codification Topic 605-45, Revenue Recognition, Principal Agent Considerations, the amounts are determinable and collection of the related receivable is reasonably assured.
Grant Revenue	'
	Grant Revenue
	The Company recognizes revenues from grants in the period in which the Company has incurred the expenditures in compliance with the specific restrictions of the grant.
	Revenue from grants was recognized in the period in which the related expenditures were incurred and totaled approximately $0.1 million and 0.4 million for the years ended December 31, 2012 and 2011, respectively, and are reflected as other revenue in the statements of operations.
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,
			2013			2012			2011
	Numerator:
	Net loss		$	(95,450	)	$	(42,949	)	$	(25,306	)
	Denominator
	Weighted average common shares(1)
	Denominator for basic calculation			28,087			22,579			2,950
	Denominator for diluted calculation			28,087			22,579			2,950
	Net loss per share:(1)
	Basic		$	(3.40	)	$	(1.90	)	$	(8.58	)
	Diluted		$	(3.40	)	$	(1.90	)	$	(8.58	)
		-1	Per share computations for fiscal 2011 are based on (i) Private Synageva’s historic common stock balances (excluding preferred stock) up to the Reverse Merger date and (ii) post-Reverse Merger common stock from the Reverse Merger date to year end.
	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,
			2013			2012			2011
	Options to purchase common stock			2,710			2,529			2,371
Recently Issued and Proposed Accounting Pronouncements	'
	Recently Issued and Proposed Accounting Pronouncements
	In February 2013, the Financial Accounting Standards Board (“FASB”) issued an accounting standard update related to Comprehensive Income: Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income. The revised standard requires companies to present information about reclassification adjustments from accumulated other comprehensive income in their annual financial statements in a single note or on the face of the financial statements. The Company adopted this standard in the first quarter of 2013 and presented this information below under the heading, Accumulated Other Comprehensive Income (Loss) to these consolidated financial statements. The adoption of this standard did not have an impact on our financial position or results of operations.
	In July 2013, the FASB issued an accounting standards update clarifying the presentation of an unrecognized tax benefit when a net operating loss carryforward, a similar tax loss, or a tax credit carryforward exists. The updated guidance requires the netting of unrecognized tax benefits against a deferred tax asset for a loss or other carryforward when settlement of the liability for an unrecognized tax benefit in this manner is available. The update is effective prospectively for reporting periods beginning after December 15, 2013, and early adoption and retrospective adoption are permitted. The adoption of this guidance is not currently expected to have a material impact on the Company’s consolidated financial statements or disclosures.
Accumulated Other Comprehensive Loss	'
	Accumulated Other Comprehensive Loss
	The following table summarizes the changes in accumulated other comprehensive income (loss), net of tax by component:
			Unrealized			Translation			Total
			Gains on			Adjustments
			Available
			for Sale
			Securities
	Balance, as of December 31, 2012			15			(9	)		6
	Other comprehensive loss before reclassifications			(37	)		(28	)		(65	)
	Amounts reclassified from accumulated other comprehensive loss			—			—			—
	Net current period other comprehensive loss			(37	)		(28	)		(65	)
	Balance, as of December 31, 2013			(22	)		(37	)		(59	)

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
Accounting Policies [Abstract]	'
Summary of Amortized Cost and Estimated Fair Values	'
	All of the Company’s investments were classified as available-for-sale at December 31, 2013 and December 31, 2012. 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, 2013:
	U.S. Treasury securities		$	346,618		$	—		$	(22	)	$	346,596
	Total		$	346,618		$	—		$	(22	)	$	346,596
	Balance at December 31, 2012:
	U.S. Treasury securities		$	195,055		$	15		$	—		$	195,070
	Total		$	195,055		$	15		$	—		$	195,070
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, 2013:
			December 31,			Quoted Price			Significant			Significant
			2013			in Active			Other			Unobservable
						Markets			Observable			Inputs
						(Level 1)			Inputs			(Level 3)
									(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		$	—
	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, 2012:
			December 31,			Quoted Price			Significant			Significant
			2012			in Active			Other			Unobservable
						Markets			Observable			Inputs
						(Level 1)			Inputs			(Level 3)
									(Level 2)
	Assets
	Cash equivalents
	Money market fund		$	10,387		$	10,387		$	—		$	—
	US treasury securities			10,011			10,011			—		$	—
	Marketable securities
	US treasury securities		$	195,070		$	195,070		$	—		$	—
	Total		$	215,468		$	215,468		$	—		$	—
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,
			2013			2012			2011
	Numerator:
	Net loss		$	(95,450	)	$	(42,949	)	$	(25,306	)
	Denominator
	Weighted average common shares(1)
	Denominator for basic calculation			28,087			22,579			2,950
	Denominator for diluted calculation			28,087			22,579			2,950
	Net loss per share:(1)
	Basic		$	(3.40	)	$	(1.90	)	$	(8.58	)
	Diluted		$	(3.40	)	$	(1.90	)	$	(8.58	)
		-1	Per share computations for fiscal 2011 are based on (i) Private Synageva’s historic common stock balances (excluding preferred stock) up to the Reverse Merger date and (ii) post-Reverse Merger common stock from the Reverse Merger date to year end.
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,
			2013			2012			2011
	Options to purchase common stock			2,710			2,529			2,371
Component of Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax	'
	The following table summarizes the changes in accumulated other comprehensive income (loss), net of tax by component:
			Unrealized			Translation			Total
			Gains on			Adjustments
			Available
			for Sale
			Securities
	Balance, as of December 31, 2012			15			(9	)		6
	Other comprehensive loss before reclassifications			(37	)		(28	)		(65	)
	Amounts reclassified from accumulated other comprehensive loss			—			—			—
	Net current period other comprehensive loss			(37	)		(28	)		(65	)
	Balance, as of December 31, 2013			(22	)		(37	)		(59	)

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2013 and 2012:
		December 31,
		2013			2012
	Laboratory equipment	$	6,228		$	3,478
	Leasehold improvements		13,923			2,748
	Computer, software and other		2,048			1,115
	Construction in process		1,713			—
			23,912			7,341
	Less: Accumulated depreciation and amortization		(6,699	)		(3,329	)
		$	17,213		$	4,012

Supplemental_Balance_Sheet_Dat1

Supplemental Balance Sheet Data (Tables)	12 Months Ended
	Dec. 31, 2013
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,
		2013		2012
	Prepaid clinical, manufacturing, and scientific costs	$	3,960	$	1,598
	Interest receivable		859		603
	Prepaid insurance		958		896
	Other		840		458
		$	6,617	$	3,555
Summary of Other Non-Current Assets	'
	Other non-current assets consist of the following:
		December 31,
		2013		2012
	Restricted cash	$	1,935	$	—
	Other		52		38
		$	1,987	$	38
Accrued Expenses	'
	Accrued expenses consist of the following:
		December 31,
		2013		2012
	Accrued compensation and benefits	$	3,244	$	1,862
	Clinical, manufacturing and scientific costs		6,587		1,978
	Professional fees		568		685
	Other		862		587
		$	11,261	$	5,112

Reverse_Merger_Tables

Reverse Merger (Tables)	12 Months Ended
	Dec. 31, 2013
Business Combinations [Abstract]	'
Schedule of Purchase Price, Based on the Stock Price as of the Reverse Merger Date	'
	The purchase price, based on the stock price as of the Reverse Merger date, was as follows:
	Fair value of Trimeris shares outstanding		$	68,767
	Fair value of vested Trimeris stock options			1,102
	Purchase price		$	69,869
Fair Value of Acquired Assets and Liabilities	'
	The fair value of acquired assets and liabilities were as follows (in thousands):
	Cash and cash equivalents		$	50,107
	Accounts receivable, taxes refundable and other current assets			4,437
	Developed technology—FUZEON			9,300
	Goodwill(1)			8,535
	Assumed liabilities			(2,510	)
	Total		$	69,869
		-1	The goodwill resulting from the Reverse Merger is not deductible for tax purposes.
Selected Unaudited Pro Forma Financial Information	'
	The following table presents selected unaudited financial information, as if the Reverse Merger with Trimeris had occurred on January 1, 2010 (in thousands, except per share data).
			Year Ended
			2011
			(Unaudited)
	Pro forma net revenue(1)		$	10,035
	Pro forma net (loss) income			(22,337	)
	Pro forma net (loss) income per common share—basic		$	(4.82	)
	Pro forma net (loss) income per common share—diluted		$	(4.82	)
		-1	Fiscal 2010 revenue includes $18.7 million of revenue resulting from entering into the Deferred Marketing Expenses Agreement with Roche, which relieved the obligation to repay certain deferred marketing expenses.

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets, Net (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2013
		Initial		Cost		Accumulated			Net
		Estimated Life				Amortization
	Developed Technology		10 years	$	9,300	$	(5,809	)	$	3,491
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)
	2014	$	1,218
	2015		847
	2016		555
	2017		361
	2018 and beyond		510

Share_Based_Payments_Tables

Share Based Payments (Tables)	12 Months Ended
	Dec. 31, 2013
Disclosure Of Compensation Related Costs Sharebased 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,
		2013			2012			2011
	Expected dividend yield		None			None			None
	Weighted average volatility in stock price		58	%		50	%		51	%
	Weighted average risk-free interest rate		1.39	%		0.88	%		1.51	%
	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 for 2013, the first year of our ESPP:
		Year Ended
		December  31,
		2013
	Expected volatility	38.5-49.6%
	Dividend yield	0.00%
	Expected life	6 months
	Risk-free interest rate	0.09-.12%
Summary of Stock Option Activity under all Equity Plans	'
	A summary of stock option activity under all equity plans for the year ended December 31, 2013, 2012, and 2011 is as follows:
		Number of			Weighted
		Shares			Average
					Exercise Price
	Outstanding at December 31, 2010		1,244		$	1.27
	Options granted		1,029			13.39
	Options assumed through merger with Trimeris		373			57.23
	Options exercised		(209	)		0.89
	Options canceled or expired		(66	)		1.41
	Outstanding at December 31, 2011		2,371		$	15.34
	Options granted		820			43.9
	Options exercised		(519	)		2.62
	Options canceled or expired		(143	)		53.83
	Outstanding at December 31, 2012		2,529		$	25.06
	Options granted		1,119			45.31
	Options exercised		(660	)		7.52
	Options canceled or expired		(278	)		60.8
	Outstanding at December 31, 2013		2,710		$	34.05
	Exercisable at December 31, 2013		1,000		$	26.39
	Exercisable and expected to vest at December 31, 2013		2,521		$	33.71
Options Outstanding and Currently Exercisable	'
	Options outstanding and currently exercisable at December 31, 2013, 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		102			5.6		$	0.94			102	$	0.94
	$1.10-$1.70		200			7.1			1.66			76		1.61
	$3.52-$8.73		160			6.2			6.08			116		5.1
	$10.10-$20.60		34			5.6			13.94			34		13.94
	$23.00-$45.50		1,701			8.5			35.69			536		31.73
	$45.51-$69.50		509			8.1			57.56			132		58.56
	$94.80-$194.00		4			0.1			94.8			4		94.8
			2,710			8		$	34.05			1,000	$	26.39
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,
		2013			2012			2011
	Research and development	$	3,586		$	1,432		$	231
	Selling, general and administrative		5,601			3,539			402
		$	9,187		$	4,971		$	633

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
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,
		2013			2012			2011
	U.S. pretax loss	$	(95,588	)	$	(43,032	)	$	(25,402	)
	Non-U.S. pretax income		186			83			96
	Loss before provision for income taxes	$	(95,402	)	$	(42,949	)	$	(25,306	)
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,
		2013			2012			2011
	Federal tax at statutory rate	$	(32,453	)	$	(14,603	)	$	(8,571	)
	State income taxes		(3,580	)		(1,149	)		(1,278	)
	State rate changes		215			2,161			(1,443	)
	Federal and state credits		(21,186	)		(15,784	)		(1,611	)
	Trimeris net operating losses		—			—			(9,481	)
	Nondeductible 162(m) compensation		2,780			—			—
	Expiration of state NOLs		46			11,129			337
	Stock-based compensation		564			335			(26	)
	Valuation allowance		53,155			17,887			22,081
	Other		507			24			(8	)
	Provision for income taxes	$	48		$	—		$	—
Significant Components of Net Deferred Tax Asset	'
	Significant components of the Company’s net deferred tax asset as December 31, 2013 and 2012 are as follows:
		2013			2012
	Deferred tax assets:
	Net operating losses	$	42,962		$	37,451
	Capitalized research and development		23,822			10,286
	Tax credit carryforwards		57,155			25,693
	Deferred revenue		87			2,056
	Accrued expenses		210			142
	Depreciation and amortization		1,787			235
	Stock-based compensation		3,411			1,289
	Other		11			10
			129,445			77,162
	Deferred tax liabilities:
	Acquired intangibles		(655	)		(1,527	)
	Valuation allowance		(128,790	)		(75,635	)
	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		2010
	State of Georgia		2010
	State of North Carolina		2010
	Commonwealth of Massachusetts		2010

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2013:
	Year Ending December 31,		Operating		Capital
			Leases		Leases
	2014		$	1,490	$	253
	2015			1,501		439
	2016			1,516		448
	2017			1,519		457
	2018			1,527		466
	2019 and beyond			1,579		2,688
	Total minimum lease payments		$	9,132	$	4,751
	Less amount representing interest					(700	)
	Present value of obligations under capital leases (1)				$	4,051
		-1	The Company’s capital lease obligation relates to the construction of a manufacturing facility in Bogart, GA. As of December 31, 2013, the Company has recorded construction in process and a facility lease obligation of $1.7 million. Upon the completion of the landlord construction in 2014, the Company estimates that the present value of the obligation will be approximately $4.1 million. The current portion of capital lease obligation was less than $0.1 million as of December 31, 2013.

Quarterly_Financial_Data_Unaud1

Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2013
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 2013 and 2012. 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,
		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
		Three Months Ended
		March 31,			June 30,			September 30,			December 31,
		2012			2012			2012			2012
		(unaudited)
	Revenue	$	2,397			2,249		$	5,428		$	4,880
	Loss from operations		(7,355	)		(10,226	)		(10,189	)		(15,251	)
	Net loss		(7,353	)		(10,223	)		(10,182	)		(15,191	)
	Loss per share, basic and diluted	$	(0.35	)	$	(0.48	)	$	(0.43	)	$	(0.62	)
	Weighted average shares outstanding, basic and diluted		20,774			21,284			23,825			24,347

Supplemental_Disclosures_of_Ca1

Supplemental Disclosures of Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2013
Supplemental Cash Flow Elements [Abstract]	'
Summary of Company's Supplemental Noncash Investing and Financing Activities	'
	The following schedule summarizes the Company’s supplemental noncash investing and financing activities that are not presented in the statement of cash flows:
		Years Ended December 31,
		2013		2012		2011
	Supplemental schedule of noncash investing and financing activities
	Capitalization of construction-in-progress related to facility lease obligation (Note 3)	$	1,713		—		—
	Capital expenditures incurred but not yet paid	$	360		—		—
	Related to Reverse Merger:
	Conversion of convertible note into preferred stock		—		—		12,500
	Conversion of preferred stock into common stock		—		—		108,081
	Payments made in common stock to underwriter		—		—		500
	Conversion of preferred stock warrants to common stock warrants		—		—		271
	Fair value of assets acquired in Merger	$	—	$	—	$	72,379
	Fair value of liabilities assumed in Merger		—		—		(2,510	)
	Fair value of net assets acquired in Merger	$	—	$	—	$	69,869

Nature_of_the_Business_Additio

Nature of the Business - Additional Information (Detail) (USD $)	12 Months Ended
Share data in Millions, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2013	Jan. 09, 2013
		Offerings	Public Offering Closing on September 2013 [Member]	Public Offering Closing on January 2013 [Member]
Nature Of Business [Line Items]	'	'	'	'
Accumulated deficit	($254,239,000)	($158,789,000)	'	'
Closure of underwritten public offering	'	'	179,100,000	117,500,000
Shares of common stock offered	'	'	3.2	2.5
Price per share of common stock offered	'	'	$56.63	$47.53
Net proceeds from public offering	'	$192,700,000	$170,100,000	$111,100,000
Number of public offerings	'	2	'	'
Cash and cash equivalent, description	'Expects that it will have sufficient cash and cash equivalents to sustain operations to at least the second half of 2015.	'	'	'

Summary_of_Significant_Account3

Summary of Significant Accounting Policies - Summary of Amortized Cost and Estimated Fair Values (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	$346,618	$195,055
Unrealized Gains	'	15
Unrealized Losses	-22	'
Fair Value	346,596	195,070
U.S. Treasury Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Amortized Cost	346,618	195,055
Unrealized Gains	'	15
Unrealized Losses	-22	'
Fair Value	$346,596	$195,070

Summary_of_Significant_Account4

Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
	Segment
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]	'	'	'
Other than temporary Investments	$0	$0	'
Collaboration and license revenue	6,332,000	7,875,000	640,000
Recognized royalty revenue	7,042,000	7,023,000	1,083,000
Revenue from Grants	'	100,000	400,000
Acquired in-process research and development	2,500,000	344,000	'
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%	'	'
Recognized royalty revenue	$7,000,000	$7,000,000	$1,100,000

Summary_of_Significant_Account5

Summary of Significant Accounting Policies - Financial Assets and Liabilities Measured at Fair Value on a Recurring Basis (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Assets	'	'
Marketable securities	$346,596	$195,070
Assets	395,516	215,468
Quoted Prices in Active Markets (Level 1) [Member]	'	'
Assets	'	'
Assets	27,899	215,468
Significant Other Observable Inputs (Level 2) [Member]	'	'
Assets	'	'
Assets	367,617	'
Significant Unobservable Inputs (Level 3) [Member]	'	'
Assets	'	'
Assets	'	'
Money Market Fund [Member]	'	'
Assets	'	'
Cash equivalents-money market fund	27,899	10,387
Money Market Fund [Member] | Quoted Prices in Active Markets (Level 1) [Member]	'	'
Assets	'	'
Cash equivalents-money market fund	27,899	10,387
Money Market Fund [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Assets	'	'
Cash equivalents-money market fund	'	'
US Treasury Securities Cash Equivalents [Member]	'	'
Assets	'	'
Cash equivalents-money market fund	21,021	10,011
US Treasury Securities Cash Equivalents [Member] | Quoted Prices in Active Markets (Level 1) [Member]	'	'
Assets	'	'
Cash equivalents-money market fund	'	10,011
US Treasury Securities Cash Equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Assets	'	'
Cash equivalents-money market fund	21,021	'
US Treasury Securities Cash Equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Assets	'	'
Cash equivalents-money market fund	'	'
US Treasury Securities Marketable Securities [Member]	'	'
Assets	'	'
Marketable securities	346,596	195,070
US Treasury Securities Marketable Securities [Member] | Quoted Prices in Active Markets (Level 1) [Member]	'	'
Assets	'	'
Marketable securities	'	195,070
US Treasury Securities Marketable Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]	'	'
Assets	'	'
Marketable securities	346,596	'
US Treasury Securities Marketable Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]	'	'
Assets	'	'
Marketable securities	'	'

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, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Numerator:	'	'	'	'	'	'	'	'	'	'	'
Net loss	($30,736)	($28,123)	($22,107)	($14,484)	($15,191)	($10,182)	($10,223)	($7,353)	($95,450)	($42,949)	($25,306)
Denominator	'	'	'	'	'	'	'	'	'	'	'
Weighted average common shares Denominator for basic calculation	'	'	'	'	'	'	'	'	28,087	22,579	2,950
Weighted average common shares Denominator for diluted calculation	'	'	'	'	'	'	'	'	28,087	22,579	2,950
Net loss per share:	'	'	'	'	'	'	'	'	'	'	'
Basic	'	'	'	'	'	'	'	'	($3.40)	($1.90)	($8.58)
Diluted	'	'	'	'	'	'	'	'	($3.40)	($1.90)	($8.58)

Summary_of_Significant_Account7

Summary of Significant Accounting Policies - Computations of Diluted Weighted Average Shares Outstanding (Detail) (Options to Purchase Common Stock [Member])	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Options to Purchase Common Stock [Member]	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]	'	'	'
Antidilutive securities excluded from computation of earnings per share, amount	2,710	2,529	2,371

Summary_of_Significant_Account8

Summary of Significant Accounting Policies - Component of Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning, balance	$6	'	'
Other comprehensive loss before reclassifications	-65	'	'
Amounts reclassified from accumulated other comprehensive loss	'	'	'
Net current period other comprehensive loss	-65	10	-4
Ending, balance	-59	6	'
Unrealized Gains on Available for Sale Securities [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning, balance	15	'	'
Other comprehensive loss before reclassifications	-37	'	'
Amounts reclassified from accumulated other comprehensive loss	'	'	'
Net current period other comprehensive loss	-37	'	'
Ending, balance	-22	'	'
Translation Adjustments [Member]	'	'	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'
Beginning, balance	-9	'	'
Other comprehensive loss before reclassifications	-28	'	'
Amounts reclassified from accumulated other comprehensive loss	'	'	'
Net current period other comprehensive loss	-28	'	'
Ending, balance	($37)	'	'

Property_and_Equipment_Estimat

Property and Equipment - Estimated Useful Life of the Related Asset (Detail)	12 Months Ended
	Dec. 31, 2013
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	12 Months Ended			3 Months Ended
In Millions, unless otherwise specified	Oct. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2013
	sqft				Laboratory Facilities [Member]
	Buildings
	acre
Number of shell buildings under lease agreement	2	'	'	'	'
Area of each shell building	35,000	'	'	'	'
Area of land in acres	12	'	'	'	'
Estimated cost for the shell buildings	$11	'	'	'	'
Facility lease obligation	'	1.7	'	'	'
Amount spend for built lab facilities	'	'	'	'	5
Amount funded by landlord included in buildout of lab facilities	'	'	'	'	1.2
Depreciation and amortization expense	'	$3.50	$1	$0.50	'

Property_and_Equipment_Summary

Property and Equipment - Summary of Property and Equipment (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]	'	'
Property plant and equipment, gross	$23,912	$7,341
Less: Accumulated depreciation and amortization	-6,699	-3,329
Property plant and equipment, Net	17,213	4,012
Laboratory Equipment [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property plant and equipment, gross	6,228	3,478
Leasehold Improvements [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property plant and equipment, gross	13,923	2,748
Computer, Software and Other [Member]	'	'
Property, Plant and Equipment [Line Items]	'	'
Property plant and equipment, gross	2,048	1,115
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, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]	'	'
Prepaid clinical, manufacturing, and scientific costs	$3,960	$1,598
Interest receivable	859	603
Prepaid insurance	958	896
Other	840	458
Total	$6,617	$3,555

Supplemental_Balance_Sheet_Dat3

Supplemental Balance Sheet Data - Summary of Other Non-Current Assets (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]	'	'
Restricted cash	$1,935	'
Other	52	38
Other assets	$1,987	$38

Supplemental_Balance_Sheet_Dat4

Supplemental Balance Sheet Data - Accrued Expenses (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Condensed Financial Information Of Parent Company Only Disclosure [Abstract]	'	'
Accrued compensation and benefits	$3,244	$1,862
Clinical, manufacturing and scientific costs	6,587	1,978
Professional fees	568	685
Other	862	587
Accrued liabilities, current	$11,261	$5,112

Reverse_Merger_Additional_Info

Reverse Merger - Additional Information (Detail) (USD $)	12 Months Ended								0 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Nov. 02, 2011	Nov. 02, 2011	Nov. 02, 2011	Nov. 02, 2011	Nov. 02, 2011	Nov. 02, 2011	Nov. 02, 2011
						Exchange Ratio [Member]	Merger Purchase Price [Member]	Common Stock [Member]	Trimeris [Member]	Trimeris [Member]	Trimeris [Member]
								Exchange Ratio [Member]		Merger Purchase Price [Member]	Common Stock [Member]
Business Acquisition [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Reverse Stock Split ratio of Trimeris common stock	'	'	'	'	'	'	'	'	5	'	'
Reverse Stock Split terms description	'As a result of the Reverse Stock Split, each five shares of Trimeris common stock issued and outstanding immediately prior to the Reverse Stock Split were automatically combined into and became one share of Trimeris common stock	'	'	'	'	'	'	'	'	'	'
Price of stock option	'	'	'	'	$15.35	'	'	'	'	'	'
Stock outstanding of Trimeris after effect of Reverse Stock Split but before Reverse Merger	'	'	'	'	4,500,000	'	'	'	'	'	'
Exchange Ratio of company's preferred stock and common stock to shares of Trimeris common stock	'	'	'	'	'	'	'	'	'	'	0.413
Shares in the combined company after acquisition of Trimeris	'	'	'	'	'	13,000,000	'	'	'	'	'
Ownership interest of former stockholders of Private Synageva in combined company after reverse merger	'	'	'	'	'	75.00%	'	'	'	'	'
Ownership interest of former stockholders of Trimeris in combined company after reverse merger	'	'	'	'	'	25.00%	'	'	'	'	'
Shares of common stock outstanding of combined company after reverse merger	30,768,000	24,467,000	'	'	'	'	'	17,500,000	'	'	'
Per share cash receivable for fractional shares on reverse split off of common stock of Trimeris	'	'	'	'	'	'	$15.35	'	'	'	'
Vesting of stock option held by employee of Trimeris common stock	'	'	'	'	'	'	'	'	400,000	'	'
Closing price of a share of Trimeris common stock	'	'	'	'	'	'	'	'	'	'	$15.35
Fair value assumption basis for stock options of Trimeris, volatility rate	'	'	'	'	'	'	'	'	'	51.00%	'
Fair value assumption basis for stock options of Trimeris, risk-free interest rate	1.39%	0.88%	1.51%	'	'	'	'	'	'	1.02%	'
Fair value assumption basis for stock options of Trimeris, Weighted average expected life	'6 years	'6 years	'6 years	'	'	'	'	'	'	'2 years 9 months 18 days	'
Transaction costs related to the Reverse Merger classified as general and administrative expense	'	'	'	'	'	'	'	'	$1.10	'	'
Pro forma acquisition cost elimination	'	'	5.2	'	'	'	'	'	'	'	'
Pro forma estimated amortization expense	'	'	$3.20	$3.20	'	'	'	'	'	'	'

Reverse_Merger_Schedule_of_Pur

Reverse Merger - Schedule of Purchase Price, Based on the Stock Price as of the Reverse Merger Date (Detail) (Trimeris [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013
Trimeris [Member]	'
Business Acquisition [Line Items]	'
Fair value of Trimeris shares outstanding	$68,767
Fair value of vested Trimeris stock options	1,102
Purchase price	$69,869

Reverse_Merger_Fair_Value_of_A

Reverse Merger - Fair Value of Acquired Assets and Liabilities (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Business Acquisition [Line Items]	'	'
Goodwill	$8,535	$8,535
Trimeris [Member]	'	'
Business Acquisition [Line Items]	'	'
Cash and cash equivalents	50,107	'
Accounts receivable, taxes refundable and other current assets	4,437	'
Developed technology-FUZEON	9,300	'
Goodwill	8,535	'
Assumed liabilities	-2,510	'
Total	$69,869	'

Reverse_Merger_Selected_Unaudi

Reverse Merger - Selected Unaudited Pro Forma Financial Information (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2011
Business Combinations [Abstract]	'
Pro forma net revenue	$10,035
Pro forma net (loss) income	($22,337)
Pro forma net (loss) income per common share - basic	($4.82)
Pro forma net (loss) income per common share - diluted	($4.82)

Reverse_Merger_Selected_Unaudi1

Reverse Merger - Selected Unaudited Pro Forma Financial Information (Parenthetical) (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2010
Business Combinations [Abstract]	'
Revenue related to Deferred Marketing Expenses Agreement with Roche included in pro forma revenue	$18.70

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets, Net - Additional Information (Detail) (USD $)	12 Months Ended
	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 expense	$2,073,000	$3,232,000	$504,000

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets, Net - Intangible Assets, Net of Accumulated Amortization (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013
In Thousands, unless otherwise specified			Developed Technology [Member]
Acquired Finite-Lived Intangible Assets [Line Items]	'	'	'
Initial Estimated Life	'	'	'10 years
Cost	'	'	$9,300
Accumulated Amortization	'	'	-5,809
Net	$3,491	$5,564	$3,491

Goodwill_and_Intangible_Assets4

Goodwill and Intangible Assets, Net - Expected Amortization Expense for the Next Four Fiscal Years (Detail) (USD $)	Dec. 31, 2013
In Thousands, unless otherwise specified
Goodwill And Intangible Assets Disclosure [Abstract]	'
2014	$1,218
2015	847
2016	555
2017	361
2018 and beyond	$510

Convertible_Notes_and_Converti1

Convertible Notes and Convertible Preferred Stock - Additional Information (Detail) (USD $)

12 Months Ended

1 Months Ended

12 Months Ended

Share data in Thousands, unless otherwise specified

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2010

Mar. 31, 2011

Dec. 31, 2010

Mar. 31, 2011

Dec. 31, 2013

Dec. 31, 2010

Dec. 31, 2010

Dec. 31, 2010

Dec. 31, 2010

Total Convertible Preferred Stock [Member]

Total Convertible Preferred Stock [Member]

2011 Convertible Notes [Member]

2011 Convertible Notes [Member]

Series A-2 Convertible Preferred Stock [Member]

Series B-2 Convertible Preferred Stock [Member]

Series C-2 Convertible Preferred Stock [Member]

Series D-2 Convertible Preferred Stock [Member]

Convertible Notes And Convertible Preferred Stock [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Preferred stock, shares authorized

'

'

'

28,000

'

'

'

'

246

4,169

3,659

18,000

Convertible preferred stock ,conversion ratio

'

'

'

'

'

0.413

'

'

'

'

'

'

Preferred stock shares outstanding

0

0

0

'

'

'

'

'

'

'

'

'

Convertible notes issued

$12,500,000

'

'

'

'

'

$12,500,000

'

'

'

'

'

Convertible note offering

'

'

'

'

$25,000,000

'

'

'

'

'

'

'

Stated percentage of Convertible Notes

'

'

'

'

'

'

'

'The 2011 Convertible Notes had no stated interest rate

'

'

'

'

Share_Based_Payments_Additiona

Share Based Payments - Additional Information (Detail) (USD $)	12 Months Ended			6 Months Ended		12 Months Ended	0 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2013	Jun. 06, 2013	Dec. 31, 2013
				Employee Stock Purchase Plan [Member]	Employee Stock Purchase Plan [Member]	Employee Stock Purchase Plan [Member]	2005 Stock Option Plan [Member]	2005 Stock Option Plan [Member]
Employee Stock Ownership Plan (ESOP) Disclosures [Line Items]	'	'	'	'	'	'	'	'
Additional number of shares of common stock available for issuance	'	'	'	'	'	'	1,500,000	'
Maximum number of shares authorized under the plan	'	'	'	'	'	'	4,900,000	'
Shares subject to outstanding awards under the plan	'	'	'	'	'	'	'	2,500,000
Shares available for grant under the plan	'	'	'	'	'	'	'	1,100,000
Common stock at a discount	'	'	'	'	'	15.00%	'	'
Share based compensation arrangement by share based payment award options 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 compensation arrangement by share based payment award shares issued	'	'	'	6,000	5,000	'	'	'
Vesting period	'4 years	'	'	'	'	'	'	'
Contractual term	'10 years	'	'	'	'	'	'	'
Weighted average grant date fair value of options granted	$23.41	$20.38	$8.11	'	'	'	'	'
Total intrinsic value of stock options exercised	$28.30	$21.20	$1	'	'	'	'	'
Unamortized compensation expense	31.5	'	'	'	'	'	'	'
Weighted average period	'2 years 8 months 12 days	'	'	'	'	'	'	'
Aggregate intrinsic value of shares outstanding	83.3	'	'	'	'	'	'	'
Aggregate intrinsic value of shares exercisable	$38.50	'	'	'	'	'	'	'

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, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'	'
Expected dividend yield	'	'	'
Weighted average volatility in stock price	58.00%	50.00%	51.00%
Weighted average risk-free interest rate	1.39%	0.88%	1.51%
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, 2013	Dec. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'
Dividend yield	'	'	'
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	38.50%	'	'
Expected volatility, maximum	49.60%	'	'
Dividend yield	0.00%	'	'
Expected life	'6 months	'	'
Risk-free interest rate, minimum	0.09%	'	'
Risk-free interest rate, maximum	0.12%	'	'

Share_Based_Payments_Summary_o

Share Based Payments - Summary of Stock Option Activity under all Equity Plans (Detail) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'	'	'
Beginning balance, Number of Shares	2,529	2,371	1,244
Options granted, Number of Shares	1,119	820	1,029
Options assumed through merger with Trimeris, Number of Shares	'	'	373
Options exercised, Number of Shares	-660	-519	-209
Options canceled or expired, Number of Shares	-278	-143	-66
Ending balance, Number of Shares	2,710	2,529	2,371
Beginning balance, Weighted Average Exercise Price	$25.06	$15.34	$1.27
Exercisable, Number of Shares	1,000	'	'
Options granted, Weighted Average Exercise Price	$45.31	$43.90	$13.39
Exercisable and expected to vest, Number of Shares	2,521	'	'
Options assumed through merger with Trimeris, Weighted Average Exercise Price	'	'	$57.23
Options exercised, Weighted Average Exercise Price	$7.52	$2.62	$0.89
Options canceled or expired, Weighted Average Exercise Price	$60.80	$53.83	$1.41
Ending balance, Weighted Average Exercise Price	$34.05	$25.06	$15.34
Exercisable, Weighted Average Exercise Price	$26.39	'	'
Exercisable and expected to vest, Weighted Average Exercise Price	$33.71	'	'

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, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'
Number of Options Outstanding	2,710
Weighted Average Remaining Contractual Life (yrs)	'8 years
Weighted Average Exercise Price, Options Outstanding	$34.05
Number of Options Exercisable	1,000
Weighted Average Exercise Price, Options Exercisable	$26.39
$ 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	102
Weighted Average Remaining Contractual Life (yrs)	'5 years 7 months 6 days
Weighted Average Exercise Price, Options Outstanding	$0.94
Number of Options Exercisable	102
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	200
Weighted Average Remaining Contractual Life (yrs)	'7 years 1 month 6 days
Weighted Average Exercise Price, Options Outstanding	$1.66
Number of Options Exercisable	76
Weighted Average Exercise Price, Options Exercisable	$1.61
$ 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	160
Weighted Average Remaining Contractual Life (yrs)	'6 years 2 months 12 days
Weighted Average Exercise Price, Options Outstanding	$6.08
Number of Options Exercisable	116
Weighted Average Exercise Price, Options Exercisable	$5.10
$ 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	34
Weighted Average Remaining Contractual Life (yrs)	'5 years 7 months 6 days
Weighted Average Exercise Price, Options Outstanding	$13.94
Number of Options Exercisable	34
Weighted Average Exercise Price, Options Exercisable	$13.94
$ 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	1,701
Weighted Average Remaining Contractual Life (yrs)	'8 years 6 months
Weighted Average Exercise Price, Options Outstanding	$35.69
Number of Options Exercisable	536
Weighted Average Exercise Price, Options Exercisable	$31.73
$ 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	509
Weighted Average Remaining Contractual Life (yrs)	'8 years 1 month 6 days
Weighted Average Exercise Price, Options Outstanding	$57.56
Number of Options Exercisable	132
Weighted Average Exercise Price, Options Exercisable	$58.56
$ 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	4
Weighted Average Remaining Contractual Life (yrs)	'1 month 6 days
Weighted Average Exercise Price, Options Outstanding	$94.80
Number of Options Exercisable	4
Weighted Average Exercise Price, Options Exercisable	$94.80

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, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total operating expenses	$9,187	$4,971	$633
Research and Development [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total operating expenses	3,586	1,432	231
Selling, General and Administrative [Member]	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'
Total operating expenses	$5,601	$3,539	$402

Defined_Contribution_Plan_Addi

Defined Contribution Plan - Additional Information (Detail) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Postemployment Benefits [Abstract]	'	'	'
Defined contribution plan recognized expense to qualify for internal revenue code	$0.50	$0.20	$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, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
U.S. pretax loss	($95,588)	($43,032)	($25,402)
Non-U.S. pretax income	186	83	96
Loss before provision for income taxes	($95,402)	($42,949)	($25,306)

Income_Taxes_Schedule_of_Effec

Income Taxes - Schedule of Effective Tax Rate Based on Federal Statutory Rate (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]	'	'	'
Federal tax at statutory rate	($32,453)	($14,603)	($8,571)
State income taxes	-3,580	-1,149	-1,278
State rate changes	215	2,161	-1,443
Federal and state credits	-21,186	-15,784	-1,611
Trimeris net operating losses	'	'	-9,481
Nondeductible 162(m) compensation	2,780	'	'
Expiration of state NOLs	46	11,129	337
Stock-based compensation	564	335	-26
Valuation allowance	53,155	17,887	22,081
Other	507	24	-8
Provision for income taxes	$48	'	'

Income_Taxes_Significant_Compo

Income Taxes - Significant Components of Net Deferred Tax Asset (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Deferred tax assets:	'	'
Net operating losses	$42,962	$37,451
Capitalized research and development	23,822	10,286
Tax credit carryforwards	57,155	25,693
Deferred revenue	87	2,056
Accrued expenses	210	142
Depreciation and amortization	1,787	235
Stock-based compensation	3,411	1,289
Other	11	10
Deferred tax assets	129,445	77,162
Deferred tax liabilities:	'	'
Acquired intangibles	-655	-1,527
Valuation allowance	-128,790	-75,635
Net deferred tax asset	'	'

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
			Commonwealth of Massachusetts [Member]	Massachusetts Life Sciences Center [Member]	Federal Tax Authority [Member]	State Tax Authority [Member]	Orphan Drug Tax Credit [Member]
Operating Loss Carryforwards [Line Items]	'	'	'	'	'	'	'
Federal net operating loss carry forwards	'	$158,100,000	'	'	'	'	'
State net operating loss carry forwards	'	110,600,000	'	'	'	'	'
Net loss carry forwards	'	'	900,000	'	'	'	'
Net operating loss carry forwards expiration year	'	'	'	'	'2018	'2014	'
Operating loss carry forwards by Reverse Merger	11,100,000	'	'	'	'	'	'
Federal orphan drug credits and federal and state research tax credit carryforwards	57,100,000	'	'	'	'	'	'
Federal orphan drug credits and federal and state research tax credit carryforwards, beginning expiration year	'2018	'	'	'	'	'	'
Federal orphan drug credits and federal and state research tax credit carryforwards, ending expiration year	'2023	'	'	'	'	'	'
Operating loss carryforwards related to deductions from stock option compensation	42,300,000	'	'	'	'	'	'
Gross deferred tax asset	77,162,000	129,445,000	'	'	'	'	4,100,000
Valuation allowance	75,635,000	128,790,000	'	'	'	'	'
Uncertain tax positions	0	0	'	'	'	'	'
Amounts for unrecognized tax benefits	0	0	'	'	'	'	'
Amount received based on projected hiring	'	'	'	700,000	'	'	'
Period of recognized grant income	'	'	'	'5 years	'	'	'
Amount recognized, related to award	'	'	'	$100,000	'	'	'

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, 2013
U.S Federal [Member]	'
Income Tax Examination [Line Items]	'
Earliest tax years that remain subject to examination by jurisdictions	'2010
State of Georgia [Member]	'
Income Tax Examination [Line Items]	'
Earliest tax years that remain subject to examination by jurisdictions	'2010
State of North Carolina [Member]	'
Income Tax Examination [Line Items]	'
Earliest tax years that remain subject to examination by jurisdictions	'2010
Commonwealth of Massachusetts [Member]	'
Income Tax Examination [Line Items]	'
Earliest tax years that remain subject to examination by jurisdictions	'2010

License_Agreements_and_Collabo1

License Agreements and Collaborations - Additional Information (Detail) (USD $)

3 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

25-May-11

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Mar. 31, 2012

Aug. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Roche License Agreement [Member]

Roche License Agreement [Member]

Roche License Agreement [Member]

Roche License Agreement [Member]

Mitsubishi Tanabe Pharma Corporation [Member]

Mitsubishi Tanabe Pharma Corporation [Member]

Mitsubishi Tanabe Pharma Corporation [Member]

Mitsubishi Tanabe Pharma Corporation [Member]

Mitsubishi Tanabe Pharma Corporation [Member]

Mitsubishi Tanabe Pharma Corporation [Member]

Mitsubishi Tanabe Pharma Corporation [Member]

Accounting

Collaborative Arrangement One [Member]

Collaborative Arrangement One [Member]

Collaborative Arrangement Two [Member]

Collaborative Arrangement Two [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

'

'

'

'

Revenue recognized under the first total

3,474,000

1,369,000

3,413,000

5,118,000

4,880,000

5,428,000

2,249,000

2,397,000

13,374,000

14,954,000

2,099,000

'

'

'

'

'

'

'

2,000,000

1,900,000

4,100,000

6,000,000

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

'

'

'

'

'

'

'

'

$7,042,000

$7,023,000

$1,083,000

'

$7,000,000

$7,000,000

$1,100,000

'

'

'

'

'

'

'

Roche License Agreement expected expiration year

'

'

'

'

'

'

'

'

'

'

'

'

'2021

'

'

'

'

'

'

'

'

'

Commitments_and_Contingencies_1

Commitments and Contingencies - Additional Information (Detail) (USD $)

12 Months Ended

1 Months Ended

3 Months Ended

12 Months Ended

Share data in Thousands, unless otherwise specified

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Apr. 30, 2013

Jun. 30, 2013

Dec. 31, 2013

Other License Agreement [Member]

Other License Agreement [Member]

Other License Agreement [Member]

University of Georgia Research Foundation [Member]

University of Georgia Research Foundation [Member]

University of Georgia Research Foundation [Member]

Shire Human Genetic Therapies Inc. and Affiliates [Member]

Shire Human Genetic Therapies Inc. and Affiliates [Member]

Other Licensing Agreements [Member]

Milestone

Operating Leases Of Lessee Future Minimum Payment Term Disclosure [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Lease expiry period

'2024

'

'

'

'

'

'

'

'

'

'

'

Rental expense

$1,600,000

$1,000,000

$700,000

'

'

'

'

'

'

'

'

'

Amendment agreement date

'

'

'

'

'

'

5-Apr-07

'

'

'

'

'

Shares issued in consideration

'

'

'

'

'

'

9

'

'

'

'

'

Payments under license agreement

'

'

'

'

'

'

0

0

0

'

'

'

Acquired in-process research and development

2,500,000

394,000

'

'

'

'

'

'

'

2,500,000

'

'

Purchase of in-process research and development

2,500,000

344,000

'

'

'

'

'

'

'

'

2,500,000

'

Number of sales based milestones obligation

'

'

'

'

'

'

'

'

'

2

'

'

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

'

'

'

'

'

'

'

'

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, 2013
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]	'
2014, Operating Leases	$1,490
2015, Operating Leases	1,501
2016, Operating Leases	1,516
2017, Operating Leases	1,519
2018, Operating Leases	1,527
2019 and beyond, Operating Leases	1,579
Total minimum lease payments, Operating Leases	9,132
2014, Capital Leases	253
2015, Capital Leases	439
2016, Capital Leases	448
2017, Capital Leases	457
2018, Capital Leases	466
2019 and beyond, Capital Leases	2,688
Total minimum lease payments, Capital Leases	4,751
Less amount representing interest	-700
Present value of obligations under capital leases	$4,051

Commitments_and_Contingencies_3

Commitments and Contingencies - Minimum Future Rentals Under Non-Cancelable Leases (Parenthetical) (Detail) (USD $)	Dec. 31, 2013
Cost related to construction and facility lease obligation	$1,700,000
Present value of the obligation	4,051,000
Current portion of capital lease obligation	253,000
Maximum [Member]	'
Current portion of capital lease obligation	$100,000

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, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly Financial Information Disclosure [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Revenue	$3,474	$1,369	$3,413	$5,118	$4,880	$5,428	$2,249	$2,397	$13,374	$14,954	$2,099
Loss from operations	-30,944	-28,196	-22,190	-14,573	-15,251	-10,189	-10,226	-7,355	-95,903	-43,021	-25,019
Net loss	($30,736)	($28,123)	($22,107)	($14,484)	($15,191)	($10,182)	($10,223)	($7,353)	($95,450)	($42,949)	($25,306)
Loss per share, basic and diluted	($1)	($1.02)	($0.81)	($0.54)	($0.62)	($0.43)	($0.48)	($0.35)	($3.40)	($1.90)	($8.58)
Weighted average shares outstanding, basic and diluted	30,751	27,491	27,280	26,826	24,347	23,825	21,284	20,774	28,087	22,579	2,950

Supplemental_Disclosures_of_Ca2

Supplemental Disclosures of Cash Flow Information - Summary of Company's Supplemental Noncash Investing and Financing Activities (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Supplemental schedule of noncash investing and financing activities	'	'	'
Capitalization of construction-in-progress related to facility lease obligation (Note 3)	$1,713	'	'
Capital expenditures incurred but not yet paid	360	'	'
Related to Reverse Merger:	'	'	'
Conversion of convertible note into preferred stock	'	'	12,500
Conversion of preferred stock into common stock	'	'	108,081
Payments made in common stock to underwriter	'	'	500
Conversion of preferred stock warrants to common stock warrants	'	'	271
Fair value of assets acquired in Merger	'	'	72,379
Fair value of liabilities assumed in Merger	'	'	-2,510
Fair value of net assets acquired in Merger	'	'	$69,869

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (Subsequent Event [Member])	0 Months Ended	1 Months Ended
	Feb. 20, 2014	Jun. 30, 2014
	sqft
Subsequent Event [Member]	'	'
Subsequent Event [Line Items]	'	'
Total leases space	80,872	'
Rent per square foot	'	22.5
Payment of rent for first two months	9,524	'
Payment of rent for the following eight months	19,048	'
Additional leases space	29,316	'