Stockholders' Equity (Deficit) - Stock-Based Compensation Related to Stock Options, Restricted Stock Awards, Restricted Stock Unit, and Employee Stock Purchases (Detail) (USD $)
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12 Months Ended | ||
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | |||
Stock-based compensation expense | $ 3,597,000 | $ 3,783,000 | $ 3,069,000 |
Research and Development [Member]
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | |||
Stock-based compensation expense | 1,538,000 | 1,801,000 | 1,331,000 |
General and Administrative [Member]
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | |||
Stock-based compensation expense | $ 2,059,000 | $ 1,982,000 | $ 1,738,000 |