Sarepta Therapeutics (SRPT) 10-Q 7 Aug 14 2014 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	6 Months Ended
	Jun. 30, 2014	Jul. 31, 2014
Document And Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	30-Jun-14	'
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q2	'
Trading Symbol	'SRPT	'
Entity Registrant Name	'Sarepta Therapeutics, Inc.	'
Entity Central Index Key	'0000873303	'
Current Fiscal Year End Date	'--12-31	'
Entity Filer Category	'Large Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	40,923,746

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current Assets:	'	'
Cash and cash equivalents	$102,754	$256,965
Short-term investments	176,785	0
Accounts receivable	5,226	3,530
Restricted investments	4,000	7,250
Other current assets	15,906	3,061
Total Current Assets	304,671	270,806
Restricted investments	647	647
Property and equipment, net of accumulated depreciation and amortization of $17,945 and $17,328 as of June 30, 2014 and December 31, 2013, respectively	20,163	15,049
Patent costs, net of accumulated amortization of $1,853 and $1,622 as of June 30, 2014 and December 31, 2013, respectively	5,387	5,042
Other assets	6,441	25
Total Assets	337,309	291,569
Current Liabilities:	'	'
Accounts payable	1,309	8,080
Accrued expenses	13,839	14,601
Current portion of long-term debt	96	92
Warrant liability	9,826	9,006
Deferred revenue	3,303	3,299
Other liabilities	1,031	888
Total Current Liabilities	29,404	35,966
Long-term debt	1,525	1,576
Deferred rent and other long-term liabilities	6,459	6,835
Total Liabilities	37,388	44,377
Commitments and contingencies	'	'
Stockholders' Equity:	'	'
Preferred stock, $.0001 par value, 3,333,333 shares authorized; none issued and outstanding	0	0
Common stock, $.0001 par value, 50,000,000 shares authorized; 40,799,692 and 37,751,920 issued and outstanding as of June 30, 2014 and December 31, 2013, respectively	4	4
Additional paid-in capital	905,335	790,424
Accumulated other comprehensive loss	-35	0
Accumulated deficit	-605,383	-543,236
Total Stockholders' Equity	299,921	247,192
Total Liabilities and Stockholders' Equity	$337,309	$291,569

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Statement Of Financial Position [Abstract]	'	'
Property and equipment, accumulated depreciation and amortization	$17,945	$17,328
Patent costs, accumulated amortization	$1,853	$1,622
Preferred stock, par value	$0.00	$0.00
Preferred stock, shares authorized	3,333,333	3,333,333
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	50,000,000	50,000,000
Common stock, issued	40,799,692	37,751,920
Common stock, outstanding	40,799,692	37,751,920

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations and Comprehensive Loss (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Income Statement [Abstract]	'	'	'	'
Revenue from research contracts and other grants	$2,583	$2,951	$8,671	$7,425
Operating expenses:	'	'	'	'
Research and development	20,641	12,984	41,547	26,746
General and administrative	12,213	7,054	22,516	13,181
Operating loss	-30,271	-17,087	-55,392	-32,502
Other income (loss):	'	'	'	'
Interest income (expense) and other, net	181	-19	280	218
Loss on change in warrant valuation	-3,784	-1,945	-7,035	-28,851
Total other loss	-3,603	-1,964	-6,755	-28,633
Net loss	-33,874	-19,051	-62,147	-61,135
Other comprehensive income (loss):	'	'	'	'
Unrealized gain (loss) on available-for-sale securities	24	0	-35	0
Total other comprehensive income (loss)	24	0	-35	0
Comprehensive loss	($33,850)	($19,051)	($62,182)	($61,135)
Net loss per share - basic and diluted	($0.85)	($0.60)	($1.60)	($1.92)
Weighted average number of common stock outstanding for computing basic and diluted net loss per share	39,862	31,984	38,847	31,899

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:	'	'
Net loss	($62,147)	($61,135)
Adjustments to reconcile net loss to net cash flows used in operating activities:	'	'
Depreciation and amortization	1,483	711
Amortization of premium on available-for-sale securities	1,127	0
Loss on abandonment of patents	52	334
Stock-based compensation	9,929	3,989
Loss on change in warrant valuation	7,035	28,851
Changes in operating assets and liabilities, net:	'	'
Net (increase) decrease in accounts receivable and other assets	-20,957	549
Net decrease in accounts payable, accrued expenses and other liabilities	-4,291	-294
Net cash used in operating activities	-67,769	-26,995
Cash flows from investing activities:	'	'
Release and maturity of restricted investments	3,250	0
Purchase of restricted investments	0	-7,807
Purchase of property and equipment	-9,841	-435
Patent costs	-628	-931
Purchase of available-for-sale securities	-226,616	0
Maturity of available-for-sale securities	48,669	0
Net cash used in investing activities	-185,166	-9,173
Cash flows from financing activities:	'	'
Proceeds from exercise of options and warrants and the sale of common stock, net of offering costs	98,771	4,915
Repayments of long-term debt	-47	-45
Other financing activities, net	0	-178
Net cash provided by financing activities	98,724	4,692
Decrease in cash and cash equivalents	-154,211	-31,476
Cash and cash equivalents:	'	'
Beginning of period	256,965	187,661
End of period	102,754	156,185
Supplemental disclosure of cash flow information:	'	'
Cash paid during the period for interest	40	102
Supplemental schedule of non-cash investing activities and financing activities:	'	'
Issuance of common stock in satisfaction of warrants and other liabilities	6,215	14,928
Tenant improvements paid by landlord	65	0
Property and equipment included in accrued expenses	422	0
Receivable for warrants exercised	$0	$2,624

BUSINESS_AND_BASIS_OF_PRESENTA

BUSINESS AND BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2014
Accounting Policies [Abstract]	'
BUSINESS AND BASIS OF PRESENTATION	'
	1. BUSINESS AND BASIS OF PRESENTATION
	Business
	Sarepta Therapeutics, Inc. and its wholly-owned subsidiaries (“Sarepta” or the “Company”) is a biopharmaceutical company focused on the discovery and development of unique RNA-based therapeutics for the treatment of rare and infectious diseases. Applying its proprietary platform technologies, the Company is able to target a broad range of diseases and disorders through distinct RNA-based mechanisms of action. The Company is focused on advancing the development of its Duchenne muscular dystrophy (“DMD”) drug candidates, including its lead product candidate, eteplirsen, for which the Company is currently conducting an ongoing open label extension study following completion of its initial Phase IIb clinical trials. The Company is also developing therapeutics for the treatment of infectious diseases.
	The Company has not generated any material revenue from product sales to date and there can be no assurance that revenue from product sales will be achieved. Even if the Company does achieve revenue from product sales, it is likely to continue to incur operating losses in the near term.
	As of June 30, 2014, the Company had $284.2 million of cash, cash equivalents and investments, consisting of $102.8 million of cash and cash equivalents, $176.8 million of short-term investments and $4.6 million of restricted investments. The Company believes that its balance of cash, cash equivalents and investments is sufficient to fund its current operational plan for the next twelve months. The government contract under which the Marburg drug candidate was being developed expired in July 2014 and the Company is currently evaluating options to continue advancing its Marburg candidate and other infectious disease research and development efforts. The Company may pursue additional cash resources through public or private financings, seek additional government contracts and establish collaborations with or license its technology to other companies.
	Basis of Presentation
	The accompanying unaudited condensed consolidated financial statements, which have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”), reflect the accounts of Sarepta Therapeutics, Inc. and its wholly-owned subsidiaries. All intercompany transactions between and among its consolidated subsidiaries have been eliminated. Management has determined that the Company operates in one segment: the development of pharmaceutical products on its own behalf or in collaboration with others. The information included in this quarterly report on Form 10-Q should be read in conjunction with the Company’s consolidated financial statements and the accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.
	Estimates and Uncertainties
	The preparation of the unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, equity, revenue, expenses and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates. Significant items subject to such estimates and assumptions include the valuation of stock-based awards and liability classified warrants, research and development expenses and revenue recognition.
	Reclassification
	The Company has revised the presentation as well as the caption of certain current liabilities within the unaudited condensed consolidated balance sheets to conform to the current period presentation. “Accrued liabilities” of $9.6 million as of December 31, 2013 is reclassified from “accounts payable” and grouped with “accrued employee compensation” of $5.0 million. “Accrued liabilities” and “accrued employee compensation” are presented as “accrued expenses” on the unaudited condensed consolidated balance sheets. This revision had no impact on total current liabilities or total liabilities.

RECENT_ACCOUNTING_PRONOUNCEMEN

RECENT ACCOUNTING PRONOUNCEMENTS	6 Months Ended
	Jun. 30, 2014
Accounting Changes And Error Corrections [Abstract]	'
RECENT ACCOUNTING PRONOUNCEMENTS	'
	2. RECENT ACCOUNTING PRONOUNCEMENTS
	In June 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-12 which requires that companies that issue stock-based awards treat a performance target that affects vesting and that could be achieved after the requisite service period as a performance condition. ASU No. 2014-12 is effective for fiscal years after December 15, 2015, with early adoption permitted. The Company has elected to adopt this ASU early but does not expect the adoption of this guidance to have a material effect on its consolidated financial statements as the performance targets of the Company’s stock-based awards with performance conditions must be achieved prior to the end of the requisite service period.
	In June 2014, the FASB issued ASU No. 2014-10, which eliminates the concept of a development stage entity (“DSE”), in its entirety from U.S. GAAP. Under existing guidance, DSEs are required to report incremental information, including inception-to-date financial information, in their financial statements. A DSE is an entity devoting substantially all of its efforts to establishing a new business and for which either planned principal operations have not yet commenced or have commenced but there have been no significant revenues generated from that business. Entities classified as DSEs will no longer be subject to these incremental reporting requirements after adopting ASU No. 2014-10. ASU No. 2014-10 is effective for fiscal years beginning after December 15, 2014, with early adoption permitted. Retrospective application is required for the elimination of incremental DSE disclosures. Prior to the issuance of ASU No. 2014-10, the Company had met the definition of a DSE since its inception. The Company has elected to adopt this ASU early and, therefore, has eliminated the incremental disclosures previously required of DSEs, starting with this Quarterly Report on Form 10-Q.
	In May 2014, the FASB issued ASU No. 2014-09, which amends the guidance for accounting for revenue from contracts with customers. This ASU supersedes the revenue recognition requirements in Accounting Standards Codification Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers. Under the new guidance, a company is required to recognize revenue when it transfers goods or renders services to customers at an amount that it expects to be entitled to in exchange for these goods or services. This guidance is effective for fiscal years beginning after December 15, 2016, with early adoption not permitted. Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application. The Company has not yet determined which adoption method it will utilize or the effect that the adoption of this guidance will have on its consolidated financial statements.
	In April 2014, the FASB issued ASU No. 2014-08, which amends guidance for reporting discontinued operations and disposals of components of an entity. The amended guidance requires that a disposal representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results or a business activity classified as held for sale should be reported as discontinued operations. The amendments also expand the disclosure requirements for discontinued operations and add new disclosure requirements for individually significant dispositions that do not qualify as discontinued operations. This guidance is effective prospectively for fiscal years beginning after December 15, 2014 (early adoption is permitted only for disposals that have not been previously reported). The Company does not expect the adoption of this guidance to have a material effect on its consolidated financial statements.

ACCOUNTS_RECEIVABLE

ACCOUNTS RECEIVABLE	6 Months Ended
	Jun. 30, 2014
Receivables [Abstract]	'
ACCOUNTS RECEIVABLE	'
	3. ACCOUNTS RECEIVABLE
	The Company’s accounts receivable primarily arise from government research contracts and other grants. They are generally stated at invoiced amount and do not bear interest. Because the accounts receivable are primarily from government agencies and historically no amounts have been written off, an allowance for doubtful accounts receivable is not considered necessary. As of June 30, 2014 and December 31, 2013, the accounts receivable balance included unbilled receivables of $3.9 million and $2.4 million, respectively. Approximately $2.5 million of the unbilled receivables as of June 30, 2014 are subject to government audit and will not be collected until the completion of the audit.

FAIR_VALUE_MEASUREMENTS

FAIR VALUE MEASUREMENTS	6 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
FAIR VALUE MEASUREMENTS	'
	4. FAIR VALUE MEASUREMENTS
	The Company has certain financial assets and liabilities that are recorded at fair value which have been classified as Level 1, 2 or 3 within the fair value hierarchy as described in the accounting standards for fair value measurements.
		•		Level 1 — quoted prices for identical instruments in active markets;
		•		Level 2 — quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, and model-derived valuations in which all significant inputs and significant value drivers are observable in active markets; and
		•		Level 3 — valuations derived from valuation techniques in which one or more significant value drivers are unobservable.
	The tables below present information about the Company’s financial assets and liabilities that are measured and carried at fair value and indicate the level within the fair value hierarchy of the valuation techniques it utilizes to determine such fair value:
			Fair Value Measurement as of June 30, 2014
			Total		Level 1		Level 2		Level 3
			(in thousands)
	Money market funds		$	277	$	277	$	—	$	—
	Commercial paper			20,650		—		20,650
	Government and government agency bonds			92,178		—		92,178		—
	Corporate bonds			71,207		—		71,207		—
	Certificates of deposit			4,647		4,647		—		—
	Total assets		$	188,959	$	4,924	$	184,035	$	—
			Fair Value Measurement as of December 31, 2013
			Total		Level 1		Level 2		Level 3
			(in thousands)
	Money market funds		$	185,000	$	185,000	$	—	$	—
	Certificates of deposit			7,897		7,897		—		—
	Total assets		$	192,897	$	192,897	$	—	$	—
			Fair Value Measurement as of June 30, 2014
			Total		Level 1		Level 2		Level 3
			(in thousands)
	Warrants		$	9,826	$	—	$	—	$	9,826
	Total liabilities		$	9,826	$	—	$	—	$	9,826
			Fair Value Measurement as of December 31, 2013
			Total		Level 1		Level 2		Level 3
			(in thousands)
	Warrants		$	9,006	$	—	$	—	$	9,006
	Total liabilities		$	9,006	$	—	$	—	$	9,006
	The Company’s assets with fair value categorized as Level 1 within the fair value hierarchy include money market funds and certificates of deposit. Money market funds are publicly traded mutual funds.
	The Company’s assets with fair value categorized as Level 2 within the fair value hierarchy consist of commercial paper, government and government agency bonds and corporate bonds. These assets have been initially valued at the transaction price and subsequently valued, at the end of each reporting period, through income-based approaches utilizing market observable data.
	The Company’s liabilities with fair value categorized as Level 3 within the fair value hierarchy consist of warrants issued in January and August 2009. The fair value of these liabilities is determined using the Black-Scholes-Merton option-pricing model, which requires the use of significant judgment and estimates for the inputs in the model. For additional information related to the determination of fair value of warrants and a reconciliation of changes in fair value, please read Note 6, Warrants of the unaudited condensed consolidated financial statements.
	The carrying amounts reported in the unaudited condensed consolidated balance sheets for cash and cash equivalents, accounts receivable and accounts payable approximate fair value because of the immediate or short-term maturity of these financial instruments. The carrying amounts reported for long-term debt approximate fair value based on market activity for other debt instruments with similar characteristics and comparable risk.

CASH_CASH_EQUIVALENTS_AND_SHOR

CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS	6 Months Ended
	Jun. 30, 2014
Cash And Cash Equivalents [Abstract]	'
CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS	'
	5. CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS
	It is the Company’s policy to mitigate credit risk in its financial assets by maintaining a well-diversified portfolio that limits the amount of exposure as to maturity and investment type. The following tables summarize the Company’s cash, cash equivalents and short-term investments for each of the periods indicated:
		As of June 30, 2014
		Amortized		Gross		Gross			Fair
		Cost		Unrealized		Unrealized			Market
				Gains		Losses			Value
		(in thousands)
	Cash and money market funds	$	95,504	$	—	$	—		$	95,504
	Commercial paper		20,649		1		—			20,650
	Government and government agency bonds		92,198		3		(23	)		92,178
	Corporate bonds		71,223		5		(21	)		71,207
	Total	$	279,574	$	9	$	(44	)	$	279,539
	As reported:
	Cash and cash equivalents		102,754		—		—			102,754
	Short-term investments		176,820		9		(44	)		176,785
	Total	$	279,574	$	9	$	(44	)	$	279,539
		As of December 31, 2013
		Amortized		Gross		Gross			Fair
		Cost		Unrealized		Unrealized			Market
				Gains		Losses			Value
		(in thousands)
	Cash and money market funds	$	256,965	$	—	$	—		$	256,965
	Total	$	256,965	$	—	$	—		$	256,965
	As reported:
	Cash and cash equivalents	$	256,965	$	—	$	—		$	256,965
	Total	$	256,965	$	—	$	—		$	256,965

WARRANTS

WARRANTS	6 Months Ended
	Jun. 30, 2014
Derivative Instruments And Hedging Activities Disclosure [Abstract]	'
WARRANTS	'
	6. WARRANTS
	The Company has periodically issued warrants in connection with certain common stock offerings. The warrants issued in January and August 2009 are classified as liabilities as opposed to equity due to their settlement terms which require settlement in registered shares. These warrants are non-cash liabilities and the Company is not required to expend any cash to settle these liabilities.
	The outstanding warrants classified as liabilities are recorded on the unaudited condensed consolidated balance sheets and are adjusted to fair value at each financial reporting period, with changes in the fair value being recorded as “Loss on change in warrant valuation” in the unaudited condensed consolidated statements of operations and comprehensive loss. Fair value is determined using the Black-Scholes-Merton option-pricing model, which requires the use of significant judgment and estimates for the inputs used in the model.
	The following table reflects the assumptions for each of the periods indicated:
			As of		As of
			June 30, 2014		December 31, 2013
	Risk-free interest rate (1)		Less than 0.1%		0.10%
	Expected dividend yield (2)		0%		0%
	Expected lives (3)		0.1 – 0.2 years		0.6 – 0.7 years
	Expected volatility (4)		48.2 – 62.1%		95.50%
	Shares underlying warrants classified as liabilities		501,494		791,508
	Market value of stock at beginning of the period		$20.37		$25.80
	Market value of stock at end of the period		$29.79		$20.37
	-1	The risk-free interest rate is estimated using an average of U.S. Treasury bill interest rates that correlate to the prevailing interest rates at the valuation date.
	-2	The expected dividend yield is zero as the Company has not paid any dividends to date and does not expect to pay dividends prior to the expiration of the warrants.
	-3	The expected lives are based on the remaining contractual lives of the related warrants at the valuation date.
	-4	The expected volatility is estimated using implied volatility in exchange-traded options associated with the Company’s common stock.
	The amounts estimated according to the Black-Scholes-Merton option-pricing model may not be indicative of the actual values realized upon the exercise of these warrants by the holders.
	The following table summarizes the reconciliation of the change in value of the Company’s liability classified warrants for each of the periods indicated:
			For the Three Months Ended						For the Six Months Ended
			June 30,						June 30,
			2014			2013			2014			2013
			(in thousands)
	Balance at beginning of the period		$	9,213		$	91,077		$	9,006		$	65,193
	Increase in value of warrants			3,784			1,945			7,035			28,851
	Reclassification to stockholders’ equity upon exercise of warrants			(3,171	)		(13,906	)		(6,215	)		(14,928	)
	Balance at end of the period		$	9,826		$	79,116		$	9,826		$	79,116
	The following table summarizes the Company’s warrant activity for each of the periods indicated:
			For the Three Months Ended June 30,												For the Six Months Ended June 30,
			2014						2013						2014					2013
			Shares			Weighted			Shares			Weighted			Shares			Weighted		Shares			Weighted
						Average						Average						Average					Average
						Exercise						Exercise						Exercise					Exercise
						Price						Price						Price					Price
	Warrants outstanding at beginning of the period			633,740		$	9.92			3,093,676		$	8.49			791,508		$	10.5		3,127,618		$	8.48
	Exercised			(132,246	)		8.87			(464,753	)		8.94			(290,014	)		9.8		(498,695	)		8.89
	Warrants outstanding at end of the period			501,494		$	10.2			2,628,923		$	8.41			501,494		$	10.2		2,628,923		$	8.41
	Warrants exercisable at end of the period			501,494		$	10.2			2,628,923		$	8.41			501,494		$	10.2		2,628,923		$	8.41
	The following table summarizes the Company’s warrants outstanding at June 30, 2014:
	Issue Date		Exercise			Outstanding			Expiration
			Price			Warrants			Date
	1/30/09		$	6.96			65,325			7/30/14
	8/25/09		$	10.68			436,169			8/31/14

ACCRUED_EXPENSES

ACCRUED EXPENSES	6 Months Ended
	Jun. 30, 2014
Payables And Accruals [Abstract]	'
ACCRUED EXPENSES	'
	7. ACCRUED EXPENSES
	The following table summarizes the Company’s accrued expenses for each of the periods indicated:
		As of		As of
		June 30,		December 31,
		2014		2013
		(in thousands)
	Accrued contract manufacturing costs	$	2,941	$	1,414
	Accrued facility-related costs		556		2,843
	Accrued contract research costs		2,240		2,785
	Accrued employee compensation costs		3,932		5,048
	Accrued professional fees		3,440		1,235
	Others		730		1,276
	Total accrued expenses	$	13,839	$	14,601

EQUITY_FINANCING

EQUITY FINANCING	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
EQUITY FINANCING	'
	8. EQUITY FINANCING
	On April 29, 2014, the Company sold 2,650,000 shares of common stock at an offering price of $38.00 per share. The Company received aggregate net proceeds of approximately $94.5 million, after deducting the underwriting discounts and offering related transaction costs.
	In January 2013, the Company sold approximately 87,000 shares of common stock through its At-The-Market offering that originally commenced in September 2012 (the “2012 ATM”). The sales in January 2013 generated $2.1 million in net proceeds and fully exhausted the sales of stock available under the 2012 ATM sales agreement.

GOVERNMENT_CONTRACTS

GOVERNMENT CONTRACTS	6 Months Ended
	Jun. 30, 2014
Contractors [Abstract]	'
GOVERNMENT CONTRACTS	'
	9. GOVERNMENT CONTRACTS
	The Company recognizes revenue from U.S. and European Union (E.U.) government research contracts and other grants during the period in which the related expenditures are incurred and presents revenue and related expenses gross in the unaudited condensed consolidated statements of operations and comprehensive loss. In the periods presented, substantially all of the revenue generated by the Company was derived from government research contracts.
	The following table summarizes the revenue for each of the Company’s contracts with the U.S. and E.U. governments for each of the periods indicated:
		For the Three Months Ended				For the Six Months Ended
		June 30,				June 30,
		2014		2013		2014		2013
		(in thousands)
	July 2010 Contract (Ebola and Marburg IV)	$	1,709	$	2,076	$	5,773	$	4,690
	August 2012 Contract (Intramuscular)		—		439		—		2,245
	November 2012 SKIP-NMD Agreement (DMD)		24		9		1,389		63
	July 2013 Children’s National Medical Center (DMD)		—		—		659		—
	Carolinas Medical Center Agreement (DMD)		850		—		850		—
	Other Agreements		—		427		—		427
	Total	$	2,583	$	2,951	$	8,671	$	7,425
	July 2010 Contract (Ebola and Marburg Intravenous administration)
	In July 2010, the Company was awarded the Department of Defense (“DoD”) contract managed by its Joint Project Manager Medical Countermeasure Systems (“JPM-MCS”) program for the advanced development of its hemorrhagic fever virus therapeutic candidates, AVI-6002 and AVI-6003, against Ebola and Marburg viruses, respectively. In February 2012, the Company announced that it received permission from the U.S. Food and Drug Administration (“FDA”) to proceed with a single oligomer from AVI-7288, one of the two components that make up AVI-6003, as the lead product candidate against Marburg virus infection. In August 2012, the Company received a stop-work order related to the Ebola virus portion of the contract and, in October 2012, the DoD terminated the Ebola portion of the contract for the convenience of the government due to government funding constraints.
	The Marburg portion of the contract is structured into four segments and has an aggregate remaining period of performance spanning approximately four years if the DoD exercises its options for all segments. Activities under the first segment began in July 2010 and included preclinical studies and Phase I studies in healthy volunteers. In February 2014, the Company announced positive safety results from the Phase I multiple ascending dose study of AVI-7288. However, in July 2014, the contract expired.
	For the three months ended June 30, 2014 and 2013, the Company recognized $1.7 million and $2.1 million, respectively, as revenue under this agreement. For the six months ended June 30, 2014 and 2013, the Company recognized $5.8 million and $4.7 million, respectively, as revenue under this agreement. Due to the expiration of the contract, only revenue for contract finalization, if any, is expected in the future.
	August 2012 Agreement (Intramuscular)
	In August 2012, the Company was awarded a contract from the JPM-MCS program. The contract was for approximately $3.9 million to evaluate the feasibility of an intramuscular route of administration using AVI-7288, the Company’s candidate for treatment of Marburg virus. The period of performance for this contract concluded in the third quarter of 2013. Accordingly, no revenue was recognized since the conclusion of the contract. For the three and six months ended June 30, 2013, the Company recognized $0.4 million and $2.2 million, respectively, as revenue under this agreement.
	European Union SKIP-NMD Agreement (DMD)
	In November 2012, the Company entered into an agreement for a collaborative research project partially funded by the E.U. Health Innovation. The agreement provides for approximately $2.5 million for research in certain development and study related activities for a DMD therapeutic. For each of the three months ended June 30, 2014 and 2013, the Company recognized less than $100 thousand as revenue under this agreement. For the six months ended June 30, 2014 and 2013, the Company recognized $1.4 million and less than $100 thousand, respectively, as revenue under this agreement. The majority of the revenue under this contract has been recognized as of June 30, 2014 and only revenue for contract finalization, if any, is expected in the future.
	July 2013 Children’s National Medical Center (“CNMC”) Agreement (DMD)
	In July 2013, the Company entered into an agreement totaling $1.3 million to provide drug products to CNMC to conduct research related to one of the Company’s DMD programs. No revenue was recognized under this agreement for the three months ended June 30, 2014 or the three and six months ended June 30, 2013. For the six months ended June 30, 2014, the Company recognized revenue of $0.7 million. Revenue under this agreement was fully recognized as of March 31, 2014.
	Carolinas Medical Center (“CMC”) Agreement (DMD)
	The Company entered into a collaboration agreement with CMC to co-develop one of the Company’s DMD programs. Under the agreement, CMC was obligated to reimburse certain preclinical costs incurred by the Company. All preclinical work was completed and the Company recognized revenue of $0.9 million for the three and six months ended June 30, 2014.

STOCKBASED_COMPENSATION

STOCK-BASED COMPENSATION	6 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
STOCK-BASED COMPENSATION	'
	10. STOCK-BASED COMPENSATION
	The Company’s equity incentive plans allow for the granting of a variety of stock awards. To date, the Company has granted stock options, restricted stock awards, restricted stock units and stock appreciation rights. The fair value of stock awards, with consideration given to estimated forfeitures, is recognized as compensation expense on a straight-line basis over the vesting period of the grants.
	Stock Options
	The Company has granted stock options with both service- and performance-based criteria. In general, stock options granted vest over four years and have a ten-year term. Through the filing of an Investigational New Drug (“IND”) application during the period, 20% of performance awards were triggered to be eligible to vest subject to the remaining service conditions of the awards. Accordingly, the Company has recognized approximately $0.6 million in stock-based compensation expense related to the options with performance-based criteria.
	The following table summarizes the Company’s stock option activity for each of the periods indicated:
			For the Three Months Ended June 30,											For the Six Months Ended June 30,
			2014						2013					2014					2013
			Shares			Weighted			Shares			Weighted		Shares			Weighted		Shares			Weighted
						Average						Average					Average					Average
						Exercise						Exercise					Exercise					Exercise
						Price						Price					Price					Price
	Grants outstanding at beginning of the period			5,273,338		$	24.27			2,694,678		$	13.35		4,190,367		$	23.46		2,522,522		$	11.76
	Granted			117,770			33.75			1,511,850			34.95		1,303,035			27.45		1,754,170			34.1
	Exercised			(26,025	)		14.64			(55,157	)		7.63		(74,604	)		11.87		(119,547	)		8.35
	Canceled or expired			(136,710	)		23.11			(175,182	)		9.43		(190,425	)		25.13		(180,956	)		9.6
	Grants outstanding at end of the period			5,228,373			24.56			3,976,189		$	21.82		5,228,373			24.56		3,976,189		$	21.82
	Grants exercisable at end of the period			1,642,252			17.75			714,247		$	11.81		1,642,252			17.75		714,247		$	11.81
	The fair values of stock options granted during the periods presented were measured on the date of grant using the Black-Scholes-Merton option-pricing model, with the following assumptions:
			For the Three Months Ended June 30,			For the Six Months Ended June 30,
			2014		2013	2014		2013
	Risk-free interest rate (1)		1.5 – 1.7%		0.7 – 1.4%	1.5 – 1.7%		0.7 – 1.4%
	Expected dividend yield (2)		0%		0%	0%		0%
	Expected lives (3)		4.9 years		5.0 years	4.9 years		5.0 years
	Expected volatility (4)		93.00%		80.0 – 84.1%	93.0 – 95.4%		80.0 – 84.1%
	-1	The risk-free interest rate is estimated using an average of Treasury bill interest rates over a historical period commensurate with the expected term of the option that correlates to the prevailing interest rates at the time of grant.
	-2	The expected dividend yield is zero as the Company has not paid any dividends to date and does not expect to pay dividends in the future.
	-3	The expected lives are estimated using expected and historical exercise behavior.
	-4	The expected volatility is estimated using a blend of calculated volatility of the Company’s common stock over a historical period and implied volatility in exchange-traded options of the Company’s common stock.
	The amounts estimated according to the Black-Scholes-Merton option-pricing model may not be indicative of the actual values realized upon the exercise of these options by the holders.
	Restricted Stock Awards (“RSA”)
	The Company grants RSAs to members of its board of directors. The weighted-average grant date fair value of RSAs is based on the market price of the Company’s common stock on the date of grant. The fair value is amortized to stock-based compensation expense on a straight-line basis over the vesting period of the grants. The following table summarizes the Company’s RSA activity for each of the periods indicated:
			For the Three Months Ended June 30,											For the Six Months Ended June 30,
			2014						2013					2014					2013
			Shares			Weighted			Shares			Weighted		Shares			Weighted		Shares			Weighted
						Average						Average					Average					Average
						Grant Date						Grant Date					Grant Date					Grant Date
						Fair Value						Fair Value					Fair Value					Fair Value
	Grants outstanding at beginning of the period			12,000		$	31.98			4,998		$	10.08		6,000		$	34.92		4,998		$	10.08
	Granted			—			—			6,000			34.92		6,000			29.03		6,000			34.92
	Vested			(6,000	)		34.92			—			—		(6,000	)	$	34.92		—			—
	Grants outstanding at end of the period			6,000		$	29.03			10,998			23.63		6,000			29.03		10,998		$	23.63
	Restricted Stock Units (“RSU”)
	The Company granted RSUs to employees in 2012. The weighted-average grant date fair value of RSUs is based on the market price of the Company’s common stock on the date of grant. The fair value is amortized to stock-based compensation expense on a straight-line basis over the vesting period of the grants. The following table summarizes the Company’s RSU activity for each of the periods indicated:
			For the Three Months Ended June 30,											For the Six Months Ended June 30,
			2014						2013					2014					2013
			Shares			Weighted			Shares			Weighted		Shares			Weighted		Shares			Weighted
						Average						Average					Average					Average
						Grant Date						Grant Date					Grant Date					Grant Date
						Fair Value						Fair Value					Fair Value					Fair Value
	Grants outstanding at beginning of the period			6,507		$	5.4			37,998		$	6.33		6,507		$	5.4		38,260		$	6.32
	Vested			(6,507	)		5.4			(24,594	)		6.83		(6,507	)		5.4		(24,594	)		6.83
	Canceled or expired			—			—			(79	)		7.16		—			—		(341	)		5.4
	Grants outstanding at end of the period			0			0			13,325		$	5.4		0			0		13,325		$	5.4
	Stock Appreciation Rights (“SAR”)
	The Company issues SARs to employees on the same terms as the stock options granted to employees. The grant date fair value of the SARs is determined using the same valuation assumptions as for the stock options described above. Stock-based compensation expense is recognized on a straight-line basis over the vesting period of the SARs. The following table summarizes the Company’s SAR activity for each of the periods indicated:
			For the Three and Six Months Ended June 30,
			2014						2013
			Shares			Weighted			Shares			Weighted
						Average						Average
						Exercise						Grant
						Price						Date Fair
												Value
	Grants outstanding at beginning of the period			170,000		$	18.18			170,000		$	18.18
Grants outstanding at end of the period			170,000		$	18.18			170,000		$	18.18
Grants exercisable at end of the period			71,666		$	17.69			—		$	18.18
Employee Stock Purchase Plan (“ESPP”)
Under the Company’s ESPP, participating employees purchase common stock through payroll deductions. The purchase price is equal to 85% of the lower of the closing price of the Company’s common stock on the first business day and the last business day of the relevant plan period. The fair values of stock purchase rights are estimated using the Black-Scholes-Merton option-pricing model. The 24-month award period will end on February 29, 2016. For the purchase period ended February 28, 2014, 21,774 shares of the Company’s common stock were purchased for total proceeds of $0.5 million.
Stock-based Compensation Expense
For the three months ended June 30, 2014 and 2013, total stock-based compensation expense was $5.6 million and $2.3 million, respectively. For the six months ended June 30, 2014 and 2013, total stock-based compensation expense was $9.9 million and $4.0 million, respectively. The following table summarizes stock-based compensation expense by function included within the unaudited condensed consolidated statements of operations and comprehensive loss:
		For the Three Months Ended						For the Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
		(in thousands)
Research and development		$	2,345		$	724		$	4,218		$	1,254
General and administrative			3,242			1,594			5,711			2,735
Total		$	5,587		$	2,318		$	9,929		$	3,989
The following table summarizes stock-based compensation expense by grant type included within the unaudited condensed consolidated statements of operations and comprehensive loss:
		For the Three Months Ended						For the Six Months Ended
		June 30,						June 30,
		2014			2013			2014			2013
		(in thousands)
Stock options		$	5,042		$	2,032		$	8,953		$	3,433
Restricted stock awards			72			27			136			39
Restricted stock units			5			111			1			228
Stock appreciation rights			146			148			293			289
Employee stock purchase plan			322			—			546			—
Total		$	5,587		$	2,318		$	9,929		$	3,989

NET_LOSS_PER_SHARE

NET LOSS PER SHARE	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
NET LOSS PER SHARE	'
	11. NET LOSS PER SHARE
	Basic net loss per share is computed by dividing net loss by the weighted-average number of shares of common stock outstanding. Diluted net loss per share is computed by dividing net loss by the weighted-average number of shares of common stock and dilutive common stock equivalents outstanding. Given that the Company recorded a net loss for each of the periods presented, there is no difference between basic and diluted net loss per share since the effect of common stock equivalents would be anti-dilutive and are, therefore, excluded from the diluted net loss per share calculation.
			For the Three Months Ended						For the Six Months Ended
			June 30,						June 30,
			2014			2013			2014			2013
			(in thousands, except per share amounts)
	Net loss		$	(33,874	)	$	(19,051	)	$	(62,147	)	$	(61,135	)
	Weighted-average number of shares of common stock and common stock equivalents outstanding:
	Weighted-average number of common stock outstanding for computing basic net loss per share			39,862			31,984			38,847			31,899
	Dilutive effect of outstanding warrants and stock awards after application of the treasury stock method*			—			—			—			—
	Weighted-average number of common stock outstanding for computing diluted net loss per share			39,862			31,984			38,847			31,899
	Net loss per share — basic and diluted		$	(0.85	)	$	(0.60	)	$	(1.60	)	$	(1.92	)
	*	For the three and six months ended June 30, 2014 and 2013, warrants, stock options, restricted stock awards, restricted stock units and stock appreciation rights to purchase approximately 5,905,867 and 6,788,000 shares of common stock were excluded from the net loss per share calculation, respectively, as their effect would have been anti-dilutive.

INCOME_TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2014
Income Tax Disclosure [Abstract]	'
INCOME TAXES	'
	12. INCOME TAXES
	As of December 31, 2013, the Company had gross deferred tax assets of $133.6 million primarily from U.S. federal and state net operating loss (“NOL”) carryforwards, U.S. federal and state research and development credit carryforwards, stock-based compensation expense and intangibles. Due to uncertainties surrounding the Company’s ability to generate future taxable income to realize these assets, a full valuation allowance has been established to offset its net deferred tax asset. Additionally, the Internal Revenue Code rules could limit the future use of the Company’s NOL and research and development credit carryforwards to offset future taxable income based on ownership changes and the value of the Company’s common stock.

COMMITMENTS_AND_CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2014
Commitments And Contingencies Disclosure [Abstract]	'
COMMITMENTS AND CONTINGENCIES	'
	13. COMMITMENTS AND CONTINGENCIES
	Lease Obligations
	In June 2013, the Company entered into a lease agreement for its headquarters located in Cambridge, Massachusetts. The agreement calls for a security deposit in the form of a letter of credit totaling $0.6 million. The Company purchased a certificate of deposit (“CD”) to meet the requirement and it was recorded as a long-term restricted investment in the unaudited condensed consolidated balance sheets as of June 30, 2014. The initial term of the lease agreement is for seven years with an average annual base rent of approximately $2.4 million.
	In November 2013, the Company entered into the first amendment of its lease agreement for its headquarters located in Cambridge, Massachusetts. The amendment modified the original lease to add an additional 15,077 square feet to its original space, increasing its total rental space for its headquarters to 61,453 square feet. The amendment calls for additional annual base rent of approximately $0.5 million, subject to a 2.5% annual increase. In January 2014, the Company entered into an agreement to sublease the 15,077 square feet of office space to an unrelated third party for an 18-month term with a total base rent of approximately $0.7 million.
	In June 2014, the Company entered into an agreement to sublease from an unrelated third party 10,939 square feet of office space with a term of less than 7 years and an annual base rent of approximately $0.3 million.
	The Company also leases laboratory and office space in Corvallis, Oregon. The annual base rent at the Corvallis, Oregon facility is approximately $0.9 million, excluding other occupancy costs, and is subject to an annual increase of 3%.
	For the three months ended June 30, 2014 and 2013, rent expense and occupancy costs under all leases totaled $0.9 million and $0.7 million, respectively. For the six months ended June 30, 2014 and 2013, rent expense and occupancy costs under all leases totaled $2.0 million and $1.3 million, respectively. The aggregate non-cancelable future minimum payments under leases were as follows:
		As of
		June 30, 2014
		(in thousands)
	2014 (6 months)	$	1,860
	2015		4,026
	2016		4,169
	2017		4,271
	2018		4,374
	Thereafter		9,566
	Total minimum lease payments	$	28,266
	Royalty Obligations
	The Company has license agreements for which it is obligated to pay minimum royalties if the Company does not terminate the relevant agreement. The notice period to terminate these agreements is six months or less. For each of the three and six months ended June 30, 2014 and 2013, royalty payments under these agreements were less than $100 thousand.
	The Company is also obligated to pay royalties upon the net sales of DMD products. The royalty rates are in the low to mid- single-digit percentages for both inside and outside the United States. For example, under the agreement with Charley’s Fund, Inc. signed in October 2007, the Company is obligated to pay a mid-single-digit percentage royalty on the net sales of any product developed pursuant to the agreement with Charley’s Fund up to a maximum of $3.4 million. In May 2003, the Company entered into a collaboration and license agreement with Ercole Biotechnology, Inc. and Isis Pharmaceuticals, Inc. (“Isis-Ercole”). The range of percentage of royalty payments under this agreement, should such payments ever be made, is from a fraction of a percent to mid-single-digit percentages.
	Milestone Obligations
	The Company has license agreements for which it is obligated to pay development and commercial milestones as a product candidate proceeds from the filing of an IND application through approval for commercial sale. There were no significant milestone payments under these agreements for the three or six months ended June 30, 2014 and 2013, respectively.
	Under the collaboration and license agreement with Isis-Ercole, the Company may be obligated to make up to $23.4 million in milestone payments. As of June 30, 2014, the Company has not made any payments under this agreement and is not under any current obligation to make any such milestone payments, as the conditions triggering any such milestone payment obligations have not been satisfied. Subject to the satisfaction of certain milestones triggering the obligation to make any such payments, Isis may be obligated to make milestone payments to the Company of up to $21.1 million in the aggregate for each product developed under a licensed patent under this agreement. As of June 30, 2014, Isis has not made and is not under any current obligation to make any such milestone payments, as the conditions triggering any such milestone payment obligations have not been satisfied.
	In April 2013, the Company and the University of Western Australia (“UWA”) entered into an agreement under which an existing exclusive license agreement between the Company and UWA was amended and restated. Under the terms of this agreement, UWA granted the Company an exclusive license to certain UWA intellectual property rights in exchange for up to $7.1 million in up-front, development and commercial milestone payments. For the three and six months ended June 30, 2014 and 2013, the Company recognized $0 and $1.0 million, respectively, relating to certain up-front payments required under the agreement as research and development expense in the unaudited condensed consolidated statement of operations and comprehensive loss.
	In March 2014, the Company entered into a patent assignment agreement with a group of scientists (collectively, “Assignors”). Under the terms of the agreement, the Assignors transferred to the Company all rights, title and interest in certain patent rights as well as technical information related to the patents. The Company may be obligated to make up to $2.7 million in development and commercial milestone payments. For the three and six months ended June 30, 2014, the Company recorded $0 and $0.3 million, respectively, relating to an up-front payment as research and development expense in the unaudited condensed consolidated statement of operations and comprehensive loss.
	Litigation
	In the normal course of business, the Company may from time to time be named as a party to various legal claims, actions and complaints, including matters involving securities, employment, intellectual property, effects from the use of therapeutics utilizing its technology, or others. For example, purported class action complaints were filed against the Company and certain of its officers in the U.S. District Court for the District of Massachusetts on January 27, 2014 and January 29, 2014. The complaints were consolidated into a single action (Corban v. Sarepta, et. al., No. 14-cv-10201) by order of the court on June 23, 2014, and plaintiffs were afforded 28 days to file a consolidated amended complaint. Plaintiffs’ consolidated amended complaint, filed on July 21, 2014, seeks to bring claims on behalf of themselves and persons or entities that purchased or acquired securities of the Company between July 10, 2013 and November 11, 2013. The consolidated amended complaint alleges that Sarepta and certain of its officers violated the federal securities laws in connection with disclosures related to eteplirsen, the Company’s lead therapeutic candidate for DMD, and seeks damages in an unspecified amount. Pursuant to the court’s June 23, 2014 order, Sarepta intends to file a motion to dismiss the consolidated amended complaint on or before August 18, 2014. Given the relatively early stages of the proceedings in the above mentioned purported claims, at this time, no assessment can be made as to the likely outcome of these claims or whether the outcomes would have a material impact on the Company.
	Purchase Commitments
	The Company has entered into long-term contractual arrangements from time to time for the provision of goods and services. The following table presents non-cancelable contractual obligations arising from these arrangements:
		As of
		June 30, 2014
		(in thousands)
	2014 (6 months)	$	38,215
	2015		42,778
	2016		40,188
	2017		23,940
	2018		5,704
	Total purchase commitments	$	150,825
	In February 2013, the Company issued two letters of credit totaling $7.3 million to a contract manufacturer in connection with certain manufacturing agreements. The obligations secured by the letters of credit are fulfilled upon payment for certain minimum volume commitments and construction milestones. To meet the requirement of the letters of credit, the Company purchased $7.3 million in CDs. One CD in the amount of $3.3 million was released and matured during the second quarter of 2014 and the other in the amount of $4.0 million with a July 2014 maturity date was recorded as a restricted investment in the unaudited condensed consolidated balance sheets as of June 30, 2014. If the minimum volume commitments have not occurred when the CD matures, the letter of credit will be extended.

SUBSEQUENT_EVENT

SUBSEQUENT EVENT	6 Months Ended
	Jun. 30, 2014
Subsequent Events [Abstract]	'
SUBSEQUENT EVENT	'
	14. SUBSEQUENT EVENT
	On May 22, 2014, the Company entered into a Purchase and Sales Agreement with Eisai, Inc. to acquire certain real and personal property located in Andover, Massachusetts. The aggregate purchase price, including certain fees and taxes is approximately $15.0 million, of which approximately $10.0 million was paid at closing and the remaining $5.0 million will be paid in two installments by July 15, 2015 and January 15, 2016. On July 15, 2014, the closing of the purchase of the real and personal property was completed.

BUSINESS_AND_BASIS_OF_PRESENTA1

BUSINESS AND BASIS OF PRESENTATION (Policies)	6 Months Ended
	Jun. 30, 2014
Accounting Policies [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying unaudited condensed consolidated financial statements, which have been prepared in accordance with accounting principles generally accepted in the United States of America (“U.S. GAAP”), reflect the accounts of Sarepta Therapeutics, Inc. and its wholly-owned subsidiaries. All intercompany transactions between and among its consolidated subsidiaries have been eliminated. Management has determined that the Company operates in one segment: the development of pharmaceutical products on its own behalf or in collaboration with others. The information included in this quarterly report on Form 10-Q should be read in conjunction with the Company’s consolidated financial statements and the accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.
Estimates and Uncertainties	'
	Estimates and Uncertainties
	The preparation of the unaudited condensed consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, equity, revenue, expenses and the disclosure of contingent assets and liabilities. Actual results could differ from those estimates. Significant items subject to such estimates and assumptions include the valuation of stock-based awards and liability classified warrants, research and development expenses and revenue recognition.
Reclassification	'
	Reclassification
	The Company has revised the presentation as well as the caption of certain current liabilities within the unaudited condensed consolidated balance sheets to conform to the current period presentation. “Accrued liabilities” of $9.6 million as of December 31, 2013 is reclassified from “accounts payable” and grouped with “accrued employee compensation” of $5.0 million. “Accrued liabilities” and “accrued employee compensation” are presented as “accrued expenses” on the unaudited condensed consolidated balance sheets. This revision had no impact on total current liabilities or total liabilities.
Recent Accounting Pronouncements	'
	In June 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-12 which requires that companies that issue stock-based awards treat a performance target that affects vesting and that could be achieved after the requisite service period as a performance condition. ASU No. 2014-12 is effective for fiscal years after December 15, 2015, with early adoption permitted. The Company has elected to adopt this ASU early but does not expect the adoption of this guidance to have a material effect on its consolidated financial statements as the performance targets of the Company’s stock-based awards with performance conditions must be achieved prior to the end of the requisite service period.
	In June 2014, the FASB issued ASU No. 2014-10, which eliminates the concept of a development stage entity (“DSE”), in its entirety from U.S. GAAP. Under existing guidance, DSEs are required to report incremental information, including inception-to-date financial information, in their financial statements. A DSE is an entity devoting substantially all of its efforts to establishing a new business and for which either planned principal operations have not yet commenced or have commenced but there have been no significant revenues generated from that business. Entities classified as DSEs will no longer be subject to these incremental reporting requirements after adopting ASU No. 2014-10. ASU No. 2014-10 is effective for fiscal years beginning after December 15, 2014, with early adoption permitted. Retrospective application is required for the elimination of incremental DSE disclosures. Prior to the issuance of ASU No. 2014-10, the Company had met the definition of a DSE since its inception. The Company has elected to adopt this ASU early and, therefore, has eliminated the incremental disclosures previously required of DSEs, starting with this Quarterly Report on Form 10-Q.
	In May 2014, the FASB issued ASU No. 2014-09, which amends the guidance for accounting for revenue from contracts with customers. This ASU supersedes the revenue recognition requirements in Accounting Standards Codification Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers. Under the new guidance, a company is required to recognize revenue when it transfers goods or renders services to customers at an amount that it expects to be entitled to in exchange for these goods or services. This guidance is effective for fiscal years beginning after December 15, 2016, with early adoption not permitted. Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application. The Company has not yet determined which adoption method it will utilize or the effect that the adoption of this guidance will have on its consolidated financial statements.
	In April 2014, the FASB issued ASU No. 2014-08, which amends guidance for reporting discontinued operations and disposals of components of an entity. The amended guidance requires that a disposal representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results or a business activity classified as held for sale should be reported as discontinued operations. The amendments also expand the disclosure requirements for discontinued operations and add new disclosure requirements for individually significant dispositions that do not qualify as discontinued operations. This guidance is effective prospectively for fiscal years beginning after December 15, 2014 (early adoption is permitted only for disposals that have not been previously reported). The Company does not expect the adoption of this guidance to have a material effect on its consolidated financial statements.

FAIR_VALUE_MEASUREMENTS_Tables

FAIR VALUE MEASUREMENTS (Tables)	6 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
Assets and Liabilities Measured and Carried at Fair Value	'
	The tables below present information about the Company’s financial assets and liabilities that are measured and carried at fair value and indicate the level within the fair value hierarchy of the valuation techniques it utilizes to determine such fair value:
		Fair Value Measurement as of June 30, 2014
		Total		Level 1		Level 2		Level 3
		(in thousands)
	Money market funds	$	277	$	277	$	—	$	—
	Commercial paper		20,650		—		20,650
	Government and government agency bonds		92,178		—		92,178		—
	Corporate bonds		71,207		—		71,207		—
	Certificates of deposit		4,647		4,647		—		—
	Total assets	$	188,959	$	4,924	$	184,035	$	—
		Fair Value Measurement as of December 31, 2013
		Total		Level 1		Level 2		Level 3
		(in thousands)
	Money market funds	$	185,000	$	185,000	$	—	$	—
	Certificates of deposit		7,897		7,897		—		—
	Total assets	$	192,897	$	192,897	$	—	$	—
		Fair Value Measurement as of June 30, 2014
		Total		Level 1		Level 2		Level 3
		(in thousands)
	Warrants	$	9,826	$	—	$	—	$	9,826
	Total liabilities	$	9,826	$	—	$	—	$	9,826
		Fair Value Measurement as of December 31, 2013
		Total		Level 1		Level 2		Level 3
		(in thousands)
	Warrants	$	9,006	$	—	$	—	$	9,006
	Total liabilities	$	9,006	$	—	$	—	$	9,006

CASH_CASH_EQUIVALENTS_AND_SHOR1

CASH, CASH EQUIVALENTS AND SHORT-TERM INVESTMENTS (Tables)	6 Months Ended
	Jun. 30, 2014
Cash And Cash Equivalents [Abstract]	'
Summary of Company Cash , Cash Equivalents and Short-Term Investments	'
	The following tables summarize the Company’s cash, cash equivalents and short-term investments for each of the periods indicated:
		As of June 30, 2014
		Amortized		Gross		Gross			Fair
		Cost		Unrealized		Unrealized			Market
				Gains		Losses			Value
		(in thousands)
	Cash and money market funds	$	95,504	$	—	$	—		$	95,504
	Commercial paper		20,649		1		—			20,650
	Government and government agency bonds		92,198		3		(23	)		92,178
	Corporate bonds		71,223		5		(21	)		71,207
	Total	$	279,574	$	9	$	(44	)	$	279,539
	As reported:
	Cash and cash equivalents		102,754		—		—			102,754
	Short-term investments		176,820		9		(44	)		176,785
	Total	$	279,574	$	9	$	(44	)	$	279,539
		As of December 31, 2013
		Amortized		Gross		Gross			Fair
		Cost		Unrealized		Unrealized			Market
				Gains		Losses			Value
		(in thousands)
	Cash and money market funds	$	256,965	$	—	$	—		$	256,965
	Total	$	256,965	$	—	$	—		$	256,965
	As reported:
	Cash and cash equivalents	$	256,965	$	—	$	—		$	256,965
	Total	$	256,965	$	—	$	—		$	256,965

WARRANTS_Tables

WARRANTS (Tables)	6 Months Ended
	Jun. 30, 2014
Reconciliation of Change in Value of Company's Warrants Liability	'
	The following table summarizes the reconciliation of the change in value of the Company’s liability classified warrants for each of the periods indicated:
			For the Three Months Ended						For the Six Months Ended
			June 30,						June 30,
			2014			2013			2014			2013
			(in thousands)
	Balance at beginning of the period		$	9,213		$	91,077		$	9,006		$	65,193
	Increase in value of warrants			3,784			1,945			7,035			28,851
	Reclassification to stockholders’ equity upon exercise of warrants			(3,171	)		(13,906	)		(6,215	)		(14,928	)
	Balance at end of the period		$	9,826		$	79,116		$	9,826		$	79,116
Summary of Warrant Activity	'
	The following table summarizes the Company’s warrant activity for each of the periods indicated:
			For the Three Months Ended June 30,												For the Six Months Ended June 30,
			2014						2013						2014					2013
			Shares			Weighted			Shares			Weighted			Shares			Weighted		Shares			Weighted
						Average						Average						Average					Average
						Exercise						Exercise						Exercise					Exercise
						Price						Price						Price					Price
	Warrants outstanding at beginning of the period			633,740		$	9.92			3,093,676		$	8.49			791,508		$	10.5		3,127,618		$	8.48
	Exercised			(132,246	)		8.87			(464,753	)		8.94			(290,014	)		9.8		(498,695	)		8.89
	Warrants outstanding at end of the period			501,494		$	10.2			2,628,923		$	8.41			501,494		$	10.2		2,628,923		$	8.41
	Warrants exercisable at end of the period			501,494		$	10.2			2,628,923		$	8.41			501,494		$	10.2		2,628,923		$	8.41
Summary of Company's Warrants Outstanding	'
	The following table summarizes the Company’s warrants outstanding at June 30, 2014:
	Issue Date		Exercise			Outstanding			Expiration
			Price			Warrants			Date
	1/30/09		$	6.96			65,325			7/30/14
	8/25/09		$	10.68			436,169			8/31/14
Warrant [Member]	'
Schedule of Assumptions	'
	The following table reflects the assumptions for each of the periods indicated:
			As of		As of
			June 30, 2014		December 31, 2013
	Risk-free interest rate (1)		Less than 0.1%		0.10%
	Expected dividend yield (2)		0%		0%
	Expected lives (3)		0.1 – 0.2 years		0.6 – 0.7 years
	Expected volatility (4)		48.2 – 62.1%		95.50%
	Shares underlying warrants classified as liabilities		501,494		791,508
	Market value of stock at beginning of the period		$20.37		$25.80
	Market value of stock at end of the period		$29.79		$20.37
	-1	The risk-free interest rate is estimated using an average of U.S. Treasury bill interest rates that correlate to the prevailing interest rates at the valuation date.
	-2	The expected dividend yield is zero as the Company has not paid any dividends to date and does not expect to pay dividends prior to the expiration of the warrants.
	-3	The expected lives are based on the remaining contractual lives of the related warrants at the valuation date.
	-4	The expected volatility is estimated using implied volatility in exchange-traded options associated with the Company’s common stock.

ACCRUED_EXPENSES_Tables

ACCRUED EXPENSES (Tables)	6 Months Ended
	Jun. 30, 2014
Payables And Accruals [Abstract]	'
Summary of Accrued Expenses	'
	The following table summarizes the Company’s accrued expenses for each of the periods indicated:
		As of		As of
		June 30,		December 31,
		2014		2013
		(in thousands)
	Accrued contract manufacturing costs	$	2,941	$	1,414
	Accrued facility-related costs		556		2,843
	Accrued contract research costs		2,240		2,785
	Accrued employee compensation costs		3,932		5,048
	Accrued professional fees		3,440		1,235
	Others		730		1,276
	Total accrued expenses	$	13,839	$	14,601

GOVERNMENT_CONTRACTS_Tables

GOVERNMENT CONTRACTS (Tables)	6 Months Ended
	Jun. 30, 2014
Contractors [Abstract]	'
Revenue from United States and European Union Governments Contracts and Other Revenue	'
	The following table summarizes the revenue for each of the Company’s contracts with the U.S. and E.U. governments for each of the periods indicated:
		For the Three Months Ended				For the Six Months Ended
		June 30,				June 30,
		2014		2013		2014		2013
		(in thousands)
	July 2010 Contract (Ebola and Marburg IV)	$	1,709	$	2,076	$	5,773	$	4,690
	August 2012 Contract (Intramuscular)		—		439		—		2,245
	November 2012 SKIP-NMD Agreement (DMD)		24		9		1,389		63
	July 2013 Children’s National Medical Center (DMD)		—		—		659		—
	Carolinas Medical Center Agreement (DMD)		850		—		850		—
	Other Agreements		—		427		—		427
	Total	$	2,583	$	2,951	$	8,671	$	7,425

STOCKBASED_COMPENSATION_Tables

STOCK-BASED COMPENSATION (Tables)	6 Months Ended
	Jun. 30, 2014
Summary of Stock Option Activity	'
	The following table summarizes the Company’s stock option activity for each of the periods indicated:
			For the Three Months Ended June 30,											For the Six Months Ended June 30,
			2014						2013					2014					2013
			Shares			Weighted			Shares			Weighted		Shares			Weighted		Shares			Weighted
						Average						Average					Average					Average
						Exercise						Exercise					Exercise					Exercise
						Price						Price					Price					Price
	Grants outstanding at beginning of the period			5,273,338		$	24.27			2,694,678		$	13.35		4,190,367		$	23.46		2,522,522		$	11.76
	Granted			117,770			33.75			1,511,850			34.95		1,303,035			27.45		1,754,170			34.1
	Exercised			(26,025	)		14.64			(55,157	)		7.63		(74,604	)		11.87		(119,547	)		8.35
	Canceled or expired			(136,710	)		23.11			(175,182	)		9.43		(190,425	)		25.13		(180,956	)		9.6
	Grants outstanding at end of the period			5,228,373			24.56			3,976,189		$	21.82		5,228,373			24.56		3,976,189		$	21.82
	Grants exercisable at end of the period			1,642,252			17.75			714,247		$	11.81		1,642,252			17.75		714,247		$	11.81
Summary of Restricted Stock Award Activity	'
	The following table summarizes the Company’s RSA activity for each of the periods indicated:
			For the Three Months Ended June 30,											For the Six Months Ended June 30,
			2014						2013					2014					2013
			Shares			Weighted			Shares			Weighted		Shares			Weighted		Shares			Weighted
						Average						Average					Average					Average
						Grant Date						Grant Date					Grant Date					Grant Date
						Fair Value						Fair Value					Fair Value					Fair Value
	Grants outstanding at beginning of the period			12,000		$	31.98			4,998		$	10.08		6,000		$	34.92		4,998		$	10.08
	Granted			—			—			6,000			34.92		6,000			29.03		6,000			34.92
	Vested			(6,000	)		34.92			—			—		(6,000	)	$	34.92		—			—
	Grants outstanding at end of the period			6,000		$	29.03			10,998			23.63		6,000			29.03		10,998		$	23.63
Summary of Restricted Stock Unit Activity	'
	The following table summarizes the Company’s RSU activity for each of the periods indicated:
			For the Three Months Ended June 30,											For the Six Months Ended June 30,
			2014						2013					2014					2013
			Shares			Weighted			Shares			Weighted		Shares			Weighted		Shares			Weighted
						Average						Average					Average					Average
						Grant Date						Grant Date					Grant Date					Grant Date
						Fair Value						Fair Value					Fair Value					Fair Value
	Grants outstanding at beginning of the period			6,507		$	5.4			37,998		$	6.33		6,507		$	5.4		38,260		$	6.32
	Vested			(6,507	)		5.4			(24,594	)		6.83		(6,507	)		5.4		(24,594	)		6.83
	Canceled or expired			—			—			(79	)		7.16		—			—		(341	)		5.4
	Grants outstanding at end of the period			0			0			13,325		$	5.4		0			0		13,325		$	5.4
Summary of Stock Appreciation Rights Activity	'
	The following table summarizes the Company’s SAR activity for each of the periods indicated:
			For the Three and Six Months Ended June 30,
			2014						2013
			Shares			Weighted			Shares			Weighted
						Average						Average
						Exercise						Grant
						Price						Date Fair
												Value
	Grants outstanding at beginning of the period			170,000		$	18.18			170,000		$	18.18
	Grants outstanding at end of the period			170,000		$	18.18			170,000		$	18.18
	Grants exercisable at end of the period			71,666		$	17.69			—		$	18.18
Summary of Stock-Based Compensation Expense by Function Included within Condensed Consolidated Statement of Operations and Comprehensive Loss	'
	The following table summarizes stock-based compensation expense by function included within the unaudited condensed consolidated statements of operations and comprehensive loss:
			For the Three Months Ended						For the Six Months Ended
			June 30,						June 30,
			2014			2013			2014			2013
			(in thousands)
	Research and development		$	2,345		$	724		$	4,218		$	1,254
	General and administrative			3,242			1,594			5,711			2,735
	Total		$	5,587		$	2,318		$	9,929		$	3,989
Summary of Stock-Based Compensation Expense by Grant Type Included within Condensed Consolidated Statement of Operations and Comprehensive Loss	'
	The following table summarizes stock-based compensation expense by grant type included within the unaudited condensed consolidated statements of operations and comprehensive loss:
			For the Three Months Ended						For the Six Months Ended
			June 30,						June 30,
			2014			2013			2014			2013
			(in thousands)
	Stock options		$	5,042		$	2,032		$	8,953		$	3,433
	Restricted stock awards			72			27			136			39
	Restricted stock units			5			111			1			228
	Stock appreciation rights			146			148			293			289
	Employee stock purchase plan			322			—			546			—
	Total		$	5,587		$	2,318		$	9,929		$	3,989
Stock Options [Member]	'
Assumptions for Measuring Fair Values of Stocks	'
	The fair values of stock options granted during the periods presented were measured on the date of grant using the Black-Scholes-Merton option-pricing model, with the following assumptions:
			For the Three Months Ended June 30,			For the Six Months Ended June 30,
			2014		2013	2014		2013
	Risk-free interest rate (1)		1.5 – 1.7%		0.7 – 1.4%	1.5 – 1.7%		0.7 – 1.4%
	Expected dividend yield (2)		0%		0%	0%		0%
	Expected lives (3)		4.9 years		5.0 years	4.9 years		5.0 years
	Expected volatility (4)		93.00%		80.0 – 84.1%	93.0 – 95.4%		80.0 – 84.1%
	-1	The risk-free interest rate is estimated using an average of Treasury bill interest rates over a historical period commensurate with the expected term of the option that correlates to the prevailing interest rates at the time of grant.
	-2	The expected dividend yield is zero as the Company has not paid any dividends to date and does not expect to pay dividends in the future.
	-3	The expected lives are estimated using expected and historical exercise behavior.
	-4	The expected volatility is estimated using a blend of calculated volatility of the Company’s common stock over a historical period and implied volatility in exchange-traded options of the Company’s common stock.

NET_LOSS_PER_SHARE_Tables

NET LOSS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Basic and Diluted Net Loss Per Share	'
			For the Three Months Ended						For the Six Months Ended
			June 30,						June 30,
			2014			2013			2014			2013
			(in thousands, except per share amounts)
	Net loss		$	(33,874	)	$	(19,051	)	$	(62,147	)	$	(61,135	)
	Weighted-average number of shares of common stock and common stock equivalents outstanding:
	Weighted-average number of common stock outstanding for computing basic net loss per share			39,862			31,984			38,847			31,899
	Dilutive effect of outstanding warrants and stock awards after application of the treasury stock method*			—			—			—			—
	Weighted-average number of common stock outstanding for computing diluted net loss per share			39,862			31,984			38,847			31,899
	Net loss per share — basic and diluted		$	(0.85	)	$	(0.60	)	$	(1.60	)	$	(1.92	)
	*	For the three and six months ended June 30, 2014 and 2013, warrants, stock options, restricted stock awards, restricted stock units and stock appreciation rights to purchase approximately 5,905,867 and 6,788,000 shares of common stock were excluded from the net loss per share calculation, respectively, as their effect would have been anti-dilutive.

COMMITMENTS_AND_CONTINGENCIES_

COMMITMENTS AND CONTINGENCIES (Tables)	6 Months Ended
	Jun. 30, 2014
Commitments And Contingencies Disclosure [Abstract]	'
Aggregate Non-Cancelable Future Minimum Payments under Leases	'
	The aggregate non-cancelable future minimum payments under leases were as follows:
		As of
		June 30, 2014
		(in thousands)
	2014 (6 months)	$	1,860
	2015		4,026
	2016		4,169
	2017		4,271
	2018		4,374
	Thereafter		9,566
	Total minimum lease payments	$	28,266
Non-cancelable Contractual Obligations	'
	The following table presents non-cancelable contractual obligations arising from these arrangements:
		As of
		June 30, 2014
		(in thousands)
	2014 (6 months)	$	38,215
	2015		42,778
	2016		40,188
	2017		23,940
	2018		5,704
	Total purchase commitments	$	150,825

Recovered_Sheet1

Business and Basis of Presentation - Additional Information (Detail) (USD $)	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
	Segment
Organization And Nature Of Business [Line Items]	'	'	'	'
Cash, cash equivalents and investments	$284,200,000	'	'	'
Cash and cash equivalents	102,754,000	256,965,000	156,185,000	187,661,000
Short-term investments	176,785,000	0	'	'
Restricted investments	4,600,000	'	'	'
Number of operating segments	1	'	'	'
Accrued liabilities	13,839,000	14,601,000	'	'
Accrued employee compensation	'	5,000,000	'	'
Accounts Payable [Member]	'	'	'	'
Organization And Nature Of Business [Line Items]	'	'	'	'
Accrued liabilities	'	$9,600,000	'	'

Accounts_Receivable_Additional

Accounts Receivable - Additional Information (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Government receivables unbilled amount	$3.90	$2.40
U.S. Government Audit [Member]	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'
Government receivables unbilled amount	$2.50	'

Assets_and_Liabilities_Measure

Assets and Liabilities Measured and Carried at Fair Value (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	$188,959	$192,897
Warrants	9,826	9,006
Total liabilities	9,826	9,006
Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	277	185,000
Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	20,650	'
Government and Government Agency Bonds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	92,178	'
Corporate Bonds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	71,207	'
Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	4,647	7,897
Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	4,924	192,897
Level 1 [Member] | Money Market Funds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	277	185,000
Level 1 [Member] | Certificates of Deposit [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	4,647	7,897
Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	184,035	'
Level 2 [Member] | Commercial Paper [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	20,650	'
Level 2 [Member] | Government and Government Agency Bonds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	92,178	'
Level 2 [Member] | Corporate Bonds [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Total assets	71,207	'
Level 3 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Warrants	9,826	9,006
Total liabilities	$9,826	$9,006

Summary_of_Company_Cash_Cash_E

Summary of Company Cash , Cash Equivalents and Short-term Investments (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Cash and Cash Equivalents [Line Items]	'	'
Cash, cash equivalents and short-term investments, Amortized cost	$279,574	$256,965
Cash, cash equivalents and short-term investments, Gross unrealized gains	9	'
Cash, cash equivalents and short-term investments, Gross unrealized losses	-44	'
Cash, cash equivalents and short-term investments, Fair market value	279,539	256,965
Cash and Cash Equivalents [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Cash, cash equivalents and short-term investments, Amortized cost	102,754	256,965
Cash, cash equivalents and short-term investments, Gross unrealized gains	'	'
Cash, cash equivalents and short-term investments, Gross unrealized losses	'	'
Cash, cash equivalents and short-term investments, Fair market value	102,754	256,965
Short-term Investments [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Cash, cash equivalents and short-term investments, Amortized cost	176,820	'
Cash, cash equivalents and short-term investments, Gross unrealized gains	9	'
Cash, cash equivalents and short-term investments, Gross unrealized losses	-44	'
Cash, cash equivalents and short-term investments, Fair market value	176,785	'
Cash and Money Market Funds [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Cash, cash equivalents and short-term investments, Amortized cost	95,504	256,965
Cash, cash equivalents and short-term investments, Gross unrealized gains	'	'
Cash, cash equivalents and short-term investments, Gross unrealized losses	'	'
Cash, cash equivalents and short-term investments, Fair market value	95,504	256,965
Commercial Paper [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Cash, cash equivalents and short-term investments, Amortized cost	20,649	'
Cash, cash equivalents and short-term investments, Gross unrealized gains	1	'
Cash, cash equivalents and short-term investments, Gross unrealized losses	'	'
Cash, cash equivalents and short-term investments, Fair market value	20,650	'
Government and Government Agency Bonds [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Cash, cash equivalents and short-term investments, Amortized cost	92,198	'
Cash, cash equivalents and short-term investments, Gross unrealized gains	3	'
Cash, cash equivalents and short-term investments, Gross unrealized losses	-23	'
Cash, cash equivalents and short-term investments, Fair market value	92,178	'
Corporate Bonds [Member]	'	'
Cash and Cash Equivalents [Line Items]	'	'
Cash, cash equivalents and short-term investments, Amortized cost	71,223	'
Cash, cash equivalents and short-term investments, Gross unrealized gains	5	'
Cash, cash equivalents and short-term investments, Gross unrealized losses	-21	'
Cash, cash equivalents and short-term investments, Fair market value	$71,207	'

Schedule_of_Assumptions_Detail

Schedule of Assumptions (Detail) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Class of Warrant or Right [Line Items]	'		'
Expected dividend yield	0.00%	[1]	0.00%	[1]
Shares underlying warrants classified as liabilities	501,494		791,508
Market value of stock at beginning of the period	$20.37		$25.80
Market value of stock at end of the period	$29.79		$20.37
Minimum [Member]	'		'
Class of Warrant or Right [Line Items]	'		'
Risk-free interest rate	0.10%	[2]	'
Expected lives	'1 month 6 days	[3]	'7 months 6 days	[3]
Expected volatility	48.20%	[4]	'
Maximum [Member]	'		'
Class of Warrant or Right [Line Items]	'		'
Risk-free interest rate	'		0.10%	[2]
Expected lives	'2 months 12 days	[3]	'8 months 12 days	[3]
Expected volatility	62.10%	[4]	95.50%	[4]
[1]	The expected dividend yield is zero as the Company has not paid any dividends to date and does not expect to pay dividends prior to the expiration of the warrants.
[2]	The risk-free interest rate is estimated using an average of U.S. Treasury bill interest rates that correlate to the prevailing interest rates at the valuation date.
[3]	The expected lives are based on the remaining contractual lives of the related warrants at the valuation date.
[4]	The expected volatility is estimated using implied volatility in exchange-traded options associated with the Company's common stock.

Schedule_of_Assumptions_Parent

Schedule of Assumptions (Parenthetical) (Detail)	6 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Fair Value Disclosures [Abstract]	'		'
Expected dividend yield	0.00%	[1]	0.00%	[1]
[1]	The expected dividend yield is zero as the Company has not paid any dividends to date and does not expect to pay dividends prior to the expiration of the warrants.

Reconciliation_of_Change_in_Va

Reconciliation of Change in Value of Company's Warrants Liability (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Class of Warrant or Right [Line Items]	'	'	'	'
Beginning balance	$9,213	$91,077	$9,006	$65,193
Increase in value of warrants	3,784	1,945	7,035	28,851
Ending balance	9,826	79,116	9,826	79,116
Warrant [Member]	'	'	'	'
Class of Warrant or Right [Line Items]	'	'	'	'
Reclassification to stockholders' equity upon exercise of warrants	($3,171)	($13,906)	($6,215)	($14,928)

Summary_of_Warrant_Activity_De

Summary of Warrant Activity (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Warrants Outstanding Shares	'	'	'	'
Warrants outstanding at beginning of the period	633,740	3,093,676	791,508	3,127,618
Exercised	-132,246	-464,753	-290,014	-498,695
Warrants outstanding at end of the period	501,494	2,628,923	501,494	2,628,923
Warrants exercisable at end of the period	501,494	2,628,923	501,494	2,628,923
Weighted Average Exercise Price	'	'	'	'
Warrants outstanding at beginning of the period	9.92	8.49	10.5	8.48
Exercised	8.87	8.94	9.8	8.89
Warrants outstanding at end of the period	10.2	8.41	10.2	8.41
Warrants exercisable at end of the period	10.2	8.41	10.2	8.41

Summary_of_Companys_Warrants_O

Summary of Company's Warrants Outstanding (Detail)	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Jun. 30, 2014	Jun. 30, 2014
							Minimum of Price Range [Member]	Maximum of Price Range [Member]
Class of Warrant or Right [Line Items]	'	'	'	'	'	'	'	'
Warrants Outstanding, Issue Date	'	'	'	'	'	'	30-Jan-09	25-Aug-09
Exercise Price of Warrants Issued	'	'	'	'	'	'	6.96	10.68
Outstanding Warrants	501,494	633,740	791,508	2,628,923	3,093,676	3,127,618	65,325	436,169
Warrant Expiration Date	'	'	'	'	'	'	30-Jul-14	31-Aug-14

Summary_of_Accrued_Expenses_De

Summary of Accrued Expenses (Detail) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Payables And Accruals [Abstract]	'	'
Accrued contract manufacturing costs	$2,941	$1,414
Accrued facility-related costs	556	2,843
Accrued contract research costs	2,240	2,785
Accrued employee compensation costs	3,932	5,048
Accrued professional fees	3,440	1,235
Others	730	1,276
Total accrued expenses	$13,839	$14,601

Equity_Financing_Additional_In

Equity Financing - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended
In Millions, except Share data, unless otherwise specified	Apr. 29, 2014	Jan. 31, 2013	Apr. 29, 2014
Equity [Abstract]	'	'	'
Common stock issued	2,650,000	87,000	'
Common stock offering price per share	'	'	$38
Net proceeds from issue of common stock	$94.50	$2.10	'

Revenue_from_United_States_and

Revenue from United States and European Union Governments Contracts and Other Revenue (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Revenue [Line Items]	'	'	'	'
U.S. and E.U. governments contract revenue	$2,583	$2,951	$8,671	$7,425
July 2010 Contract (Ebola and Marburg IV) [Member]	'	'	'	'
Revenue [Line Items]	'	'	'	'
U.S. and E.U. governments contract revenue	1,709	2,076	5,773	4,690
August 2012 Agreement (Intramuscular) [Member]	'	'	'	'
Revenue [Line Items]	'	'	'	'
U.S. and E.U. governments contract revenue	'	439	'	2,245
November 2012 SKIP-NMD Agreement (DMD) [Member]	'	'	'	'
Revenue [Line Items]	'	'	'	'
U.S. and E.U. governments contract revenue	24	9	1,389	63
Children's National Medical Center [Member]	'	'	'	'
Revenue [Line Items]	'	'	'	'
U.S. and E.U. governments contract revenue	0	0	659	0
Carolinas Medical Center Agreement [Member]	'	'	'	'
Revenue [Line Items]	'	'	'	'
U.S. and E.U. governments contract revenue	850	'	850	'
Other Agreements [Member]	'	'	'	'
Revenue [Line Items]	'	'	'	'
U.S. and E.U. governments contract revenue	'	$427	'	$427

Government_Contracts_Additiona

Government Contracts - Additional Information (Detail) (USD $)

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

0 Months Ended

3 Months Ended

6 Months Ended

1 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

1 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Aug. 29, 2012

Jun. 30, 2013

Jun. 30, 2013

Nov. 30, 2012

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2013

Jul. 31, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2014

July 2010 Contract (Ebola and Marburg IV) [Member]

July 2010 Contract (Ebola and Marburg IV) [Member]

July 2010 Contract (Ebola and Marburg IV) [Member]

July 2010 Contract (Ebola and Marburg IV) [Member]

August 2012 Agreement (Intramuscular) [Member]

August 2012 Agreement (Intramuscular) [Member]

August 2012 Agreement (Intramuscular) [Member]

November 2012 SKIP-NMD Agreement (DMD) [Member]

November 2012 SKIP-NMD Agreement (DMD) [Member]

November 2012 SKIP-NMD Agreement (DMD) [Member]

November 2012 SKIP-NMD Agreement (DMD) [Member]

November 2012 SKIP-NMD Agreement (DMD) [Member]

November 2012 SKIP-NMD Agreement (DMD) [Member]

November 2012 SKIP-NMD Agreement (DMD) [Member]

November 2012 SKIP-NMD Agreement (DMD) [Member]

Children's National Medical Center [Member]

Children's National Medical Center [Member]

Children's National Medical Center [Member]

Children's National Medical Center [Member]

Children's National Medical Center [Member]

Carolinas Medical Center Agreement [Member]

Carolinas Medical Center Agreement [Member]

Segment

Maximum [Member]

Maximum [Member]

Maximum [Member]

Accounts, Notes, Loans and Financing Receivable [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of segments

'

'

'

'

'

'

4

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Period of performance spanning

'

'

'

'

'

'

'4 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Agreement revenue

$2,583,000

$2,951,000

$8,671,000

$7,425,000

$1,709,000

$2,076,000

$5,773,000

$4,690,000

'

$439,000

$2,245,000

'

$24,000

$9,000

$1,389,000

$63,000

$100,000

$100,000

$100,000

'

$0

$0

$659,000

$0

$850,000

$850,000

Advance payments received on contracts awarded

'

'

'

'

'

'

'

'

3,900,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Agreement amount

'

'

'

'

'

'

'

'

'

'

'

$2,500,000

'

'

'

'

'

'

'

$1,300,000

'

'

'

'

'

'

StockBased_Compensation_Additi

Stock-Based Compensation - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended		6 Months Ended				0 Months Ended	6 Months Ended
	Apr. 29, 2014	Jan. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2014	Feb. 28, 2014	Jun. 30, 2014
							Performance-Based [Member]	Investigational New Drug [Member]	Employee Stock Purchase Plan [Member]	Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'	'	'	'	'
Share based compensation granted under plan vest period	'	'	'	'	'4 years	'	'	'	'	'
Term of award	'	'	'	'	'10 years	'	'	'	'	'
Stock-based compensation expense	'	'	$5,587,000	$2,318,000	$9,929,000	$3,989,000	$600,000	'	'	'
Percentage of performance award	'	'	'	'	'	'	'	20.00%	'	'
Percentage of closing price of common stock	'	'	'	'	'	'	'	'	'	85.00%
Common stock purchase	'	'	'	'	'	'	'	'	21,774	'
Proceeds from issuance of common stock	$94,500,000	$2,100,000	'	'	'	'	'	'	$500,000	'

Summary_of_Stock_Option_Activi

Summary of Stock Option Activity (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Stock Option Shares	'	'	'	'
Grants outstanding at beginning of the period	5,273,338	2,694,678	4,190,367	2,522,522
Granted	117,770	1,511,850	1,303,035	1,754,170
Exercised	-26,025	-55,157	-74,604	-119,547
Canceled or expired	-136,710	-175,182	-190,425	-180,956
Grants outstanding at end of the period	5,228,373	3,976,189	5,228,373	3,976,189
Grants exercisable at end of the period	1,642,252	714,247	1,642,252	714,247
Weighted Average Exercise Price	'	'	'	'
Grants outstanding at beginning of the period	$24.27	$13.35	$23.46	$11.76
Granted	$33.75	$34.95	$27.45	$34.10
Exercised	$14.64	$7.63	$11.87	$8.35
Canceled or expired	$23.11	$9.43	$25.13	$9.60
Grants outstanding at end of the period	$24.56	$21.82	$24.56	$21.82
Grants exercisable at end of the period	$17.75	$11.81	$17.75	$11.81

Assumptions_for_Measuring_Fair

Assumptions for Measuring Fair Values of Stocks (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Expected dividend yield	'	'	0.00%	'
Stock Options [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Risk-free interest rate	1.50%	0.70%	1.50%	0.70%
Risk-free interest rate	1.70%	1.40%	1.70%	1.40%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Expected lives	'4 years 10 months 24 days	'5 years	'4 years 10 months 24 days	'5 years
Expected volatility	'	80.00%	93.00%	80.00%
Expected volatility	'	84.10%	95.40%	84.10%
Expected volatility	93.00%	'	'	'

Assumptions_for_Measuring_Fair1

Assumptions for Measuring Fair Values of Stocks (Parenthetical) (Detail)	6 Months Ended
	Jun. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]	'
Expected dividend yield	0.00%

Summary_of_Restricted_Stock_Aw

Summary of Restricted Stock Award Activity (Detail) (Restricted Stock Awards (RSA) [Member], USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Restricted Stock Awards (RSA) [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Shares, Grants outstanding at beginning of the period	12,000	4,998	6,000	4,998
Shares, Granted	'	6,000	6,000	6,000
Shares, Vested	-6,000	'	-6,000	'
Shares, Grants outstanding at end of the period	6,000	10,998	6,000	10,998
Weighted Average Grant Date Fair Value per Share, Grants outstanding at beginning of the period	$31.98	$10.08	$34.92	$10.08
Weighted Average Grant Date Fair Value per Share, Granted	'	$34.92	$29.03	$34.92
Weighted Average Grant Date Fair Value per Share, Vested	$34.92	'	$34.92	'
Weighted Average Grant Date Fair Value per Share, Grants outstanding at end of the period	$29.03	$23.63	$29.03	$23.63

Summary_of_Restricted_Stock_Un

Summary of Restricted Stock Unit Activity (Detail) (Restricted Stock Units (RSU) [Member], USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Restricted Stock Units (RSU) [Member]	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'
Weighted Average Grant Date Fair Value per Share, Grants outstanding at beginning of the period	$5.40	$6.33	$5.40	$6.32
Weighted Average Grant Date Fair Value per Share, Vested	$5.40	$6.83	$5.40	$6.83
Weighted Average Grant Date Fair Value per Share, Canceled or expired	'	$7.16	'	$5.40
Weighted Average Grant Date Fair Value per Share, Grants outstanding at end of the period	$0	$5.40	$0	$5.40
Shares, Grants outstanding at beginning of the period	6,507	37,998	6,507	38,260
Shares, Vested	-6,507	-24,594	-6,507	-24,594
Shares, Canceled or expired	'	-79	'	-341
Shares, Grants outstanding at end of the period	0	13,325	0	13,325

Summary_of_Stock_Appreciation_

Summary of Stock Appreciation Rights Activity (Detail) (Stock Appreciation Rights [Member], USD $)	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012
Stock Appreciation Rights [Member]	'	'	'	'	'	'
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]	'	'	'	'	'	'
Shares, Grants outstanding at beginning of the period	170,000	170,000	170,000	170,000	170,000	170,000
Shares, Grants outstanding at end of the period	170,000	170,000	170,000	170,000	170,000	170,000
Shares, Grants exercisable at end of the period	71,666	'	'	'	'	'
Weighted Average Exercise Price per Share, Grants outstanding at beginning of the period	$18.18	$18.18	$18.18	$18.18	$18.18	$18.18
Weighted Average Exercise Price per Share, Grants outstanding at end of the period	$18.18	$18.18	$18.18	$18.18	$18.18	$18.18
Grants exercisable at end of the period	$17.69	'	'	$18.18	'	'

Summary_of_StockBased_Compensa

Summary of Stock-Based Compensation Expense by Function Included within Condensed Consolidated Statement of Operations and Comprehensive Loss (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	$5,587	$2,318	$9,929	$3,989
Research and Development Expenses [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	2,345	724	4,218	1,254
General and Administrative Expenses [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	$3,242	$1,594	$5,711	$2,735

Summary_of_StockBased_Compensa1

Summary of Stock-Based Compensation Expense by Grant Type Included within Condensed Consolidated Statement of Operations and Comprehensive Loss (Detail) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	$5,587	$2,318	$9,929	$3,989
Stock Options [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	5,042	2,032	8,953	3,433
Restricted Stock Awards (RSA) [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	72	27	136	39
Restricted Stock Units (RSU) [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	5	111	1	228
Stock Appreciation Rights [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	146	148	293	289
Employee Stock Purchase Plan [Member]	'	'	'	'
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]	'	'	'	'
Share-based compensation expense	$322	'	$546	'

Basic_and_Diluted_Net_Loss_Per

Basic and Diluted Net Loss Per Share (Detail) (USD $)	3 Months Ended				6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Earnings Per Share [Abstract]	'		'		'		'
Net loss	($33,874)		($19,051)		($62,147)		($61,135)
Weighted-average number of shares of common stock and common stock equivalents outstanding:	'		'		'		'
Weighted-average number of common stock outstanding for computing basic net loss per share	39,862		31,984		38,847		31,899
Dilutive effect of outstanding warrants and stock awards after application of the treasury stock method	0	[1]	0	[1]	0	[1]	0	[1]
Weighted-average number of common stock outstanding for computing diluted net loss per share	39,862		31,984		38,847		31,899
Net loss per share - basic and diluted	($0.85)		($0.60)		($1.60)		($1.92)
[1]	For the three and six months ended June 30, 2014 and 2013, warrants, stock options, restricted stock awards, restricted stock units and stock appreciation rights to purchase approximately 5,905,867 and 6,788,000 shares of common stock were excluded from the net loss per share calculation, respectively, as their effect would have been anti-dilutive.

Basic_and_Diluted_Net_Loss_Per1

Basic and Diluted Net Loss Per Share (Parenthetical) (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share [Abstract]	'	'	'	'
Anti-dilutive securities excluded from computation of earning per share	5,905,867	6,788,000	5,905,867	6,788,000

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (USD $)	Dec. 31, 2013
In Millions, unless otherwise specified
Income Tax Disclosure [Abstract]	'
Deferred tax assets, gross	$133.60

Recovered_Sheet2

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

1 Months Ended

3 Months Ended

6 Months Ended

3 Months Ended

6 Months Ended

1 Months Ended

6 Months Ended

6 Months Ended

Nov. 30, 2013

Apr. 30, 2013

Feb. 28, 2013

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

Jun. 30, 2013

Dec. 31, 2013

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2014

Jan. 31, 2014

Jun. 30, 2014

Jun. 30, 2014

Jun. 30, 2013

Jun. 30, 2014

sqft

CreditFacility

Assignors [Member]

Assignors [Member]

Sublease [Member]

Sublease [Member]

Sublease [Member]

Lease Agreements [Member]

Lease Agreements [Member]

Corvallis, Oregon [Member]

sqft

sqft

Maximum [Member]

Commitments and Contingencies [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Letters of credit amount issued

'

'

$7,300,000

'

'

'

'

'

'

'

'

'

'

'

$600,000

'

Lease agreement, expiration period

'

'

'

'

'

'

'

'

'

'

'

'

'

'7 years

'

'

Lease agreement, average base rent due current

'

'

'

4,026,000

'

4,026,000

'

'

'

'

'

'

'

2,400,000

'

'

Lease agreement, average annual base rent year two

'

'

'

4,169,000

'

4,169,000

'

'

'

'

'

'

'

2,400,000

'

'

Lease agreement, average annual base rent year three

'

'

'

4,271,000

'

4,271,000

'

'

'

'

'

'

'

2,400,000

'

'

Lease agreement, average annual base rent year four

'

'

'

4,374,000

'

4,374,000

'

'

'

'

'

'

'

2,400,000

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'

Lease agreement, average base rent year five

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'

'

'

'

'

'

'

'

'

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2,400,000

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'

Lease agreement, average base rent year six

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'

'

'

'

'

'

'

'

'

'

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'

2,400,000

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'

Lease agreement, average base rent year seven

'

'

'

'

'

'

'

'

'

'

'

'

'

2,400,000

'

'

Additional rental space under amendment

15,077

'

'

'

'

'

'

'

'

'

10,939

15,077

'

'

'

'

Total rental space

61,453

'

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'

'

'

'

'

'

'

'

'

'

'

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'

Additional annual base rent

500,000

'

'

'

'

'

'

'

'

'

'

'

'

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'

'

Percentage of annual increase in lease

2.50%

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'

'

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'

'

'

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3.00%

Lease agreement period

'

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'

'

'

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'18 months

'7 years

'

'

'

Total subleases base rent

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'

'

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'

'

300,000

700,000

'

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'

'

Annual base rent

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

900,000

Rent expense under leases

'

'

'

900,000

700,000

2,000,000

1,300,000

'

'

'

'

'

'

'

'

'

Notice period to terminate license agreements

'

'

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'

'

'6 months

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'

'

'

'

'

'

'

'

'

Royalty payments

'

'

'

100,000

100,000

100,000

100,000

'

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'

'

'

'

'

'

'

Maximum royalty to Charley's Fund

'

'

'

'

'

3,400,000

'

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'

'

'

'

'

'

'

'

Upfront and development significant milestone payments

'

'

'

0

0

0

0

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'

'

'

'

'

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'

'

Obligated to make milestone payments

'

'

'

'

'

23,400,000

'

'

'

'

'

'

'

'

'

'

Receivables under satisfaction of milestones

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'

'

'

'

21,100,000

'

'

'

'

'

'

'

'

'

'

Upfront payments recognized under agreement

'

7,100,000

'

0

1,000,000

0

1,000,000

'

0

300,000

'

'

'

'

'

'

Development and commercial milestone payments

'

'

'

'

'

'

'

'

'

2,700,000

'

'

'

'

'

'

Law affected under lawsuit filling

'

'

'

'

'

'The complaints allege that the defendants violated the federal securities laws in connection with disclosures related to eteplirsen

'

'

'

'

'

'

'

'

'

'

Number of days to amend plaintiffs complaint

'

'

'

'

'

'28 days

'

'

'

'

'

'

'

'

'

'

Certificate of deposit purchased

'

'

7,300,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Certificate of deposit maturity date

'

'

'

'

'

'2014-07

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'

'

'

'

'

'

'

'

'

Maturity of restricted investments

'

'

'

3,300,000

'

3,250,000

0

'

'

'

'

'

'

'

'

'

Restricted investments

'

'

'

$4,000,000

'

$4,000,000

'

$7,250,000

'

'

'

'

'

'

'

'

Number of letter of credit

'

'

2

'

'

'

'

'

'

'

'

'

'

'

'

'

Aggregate_NonCancelable_Future

Aggregate Non-Cancelable Future Minimum Payments under Leases (Detail) (USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
Debt Disclosure [Abstract]	'
2014 (6 months)	$1,860
2015	4,026
2016	4,169
2017	4,271
2018	4,374
Thereafter	9,566
Total minimum lease payments	$28,266

Noncancelable_Contractual_Obli

Non-cancelable Contractual Obligations (Detail) (USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
Commitments And Contingencies Disclosure [Abstract]	'
2014 (6 months)	$38,215
2015	42,778
2016	40,188
2017	23,940
2018	5,704
Total purchase commitments	$150,825

Subsequent_Event_Additional_In

Subsequent Event - Additional Information (Detail) (USD $)	6 Months Ended			0 Months Ended
In Millions, unless otherwise specified	Jun. 30, 2014	22-May-14	Jun. 30, 2014	Jul. 15, 2014
			July 15, 2015 and January 15, 2016 [Member]	Subsequent Event [Member]
Subsequent Event [Line Items]	'	'	'	'
Aggregate purchase price, including certain fees and taxes	'	$15	'	'
Purchase price, paid at closing	'	'	'	10
Purchase price, remaining amount	'	'	$5	'
Purchase and sales agreement date	22-May-14	'	'	'