Stock-Based Compensation Expense Related to Common Stock Options, Restricted Common Stock and Common Stock Warrants (Detail) (USD $)
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12 Months Ended | 162 Months Ended | |
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2013
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | |||
Stock-based compensation expense | $ 3,789,000 | $ 2,792,000 | $ 16,163,000 |
Research and development
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | |||
Stock-based compensation expense | 991,000 | 922,000 | |
General and administrative
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | |||
Stock-based compensation expense | $ 2,798,000 | $ 1,870,000 |