Exercise price of the warrants.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Section 13

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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-SubTopic 10

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Collaboration and Financing Agreements - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended
	Jul. 31, 2011	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Debt Instrument [Line Items]
Common stock issued and sold to Healthcare Royalty, amount		$ 153us-gaap_CommonStockValue		$ 153us-gaap_CommonStockValue
Common stock issued and sold to Healthcare Royalty, shares		153,365,000us-gaap_CommonStockSharesIssued		153,363,000us-gaap_CommonStockSharesIssued
Warrant exercisable to Healthcare Royalty, shares	225,000
Warrant exercisable to Healthcare Royalty, price per share (usd per share)	$ 9.00invest_InvestmentWarrantsExercisePrice
Repayment of debt		343us-gaap_RepaymentsOfDebt	0us-gaap_RepaymentsOfDebt
Change in fair value		(1,000)
Embedded Derivative Liabilities [Member]
Debt Instrument [Line Items]
Fair value of embedded derivatives		52,000		53,000
Common Stock Warrant Liabilities [Member]
Debt Instrument [Line Items]
Fair value of embedded derivatives		$ 4,683		$ 5,093