Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail)

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Summary of Significant Accounting Policies - Schedule of Fair Value Assets and Liabilities Measured on Recurring Basis (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total assets measured at fair value $ 41,545
Total liabilities measured at fair value 8,766
Warrant liability [Member]
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total liabilities measured at fair value 8,766
Money market funds [Member]
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total assets measured at fair value 15,275
Corporate debt and asset backed securities [Member]
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total assets measured at fair value 26,270
Level 1 [Member]
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total assets measured at fair value 15,275
Level 1 [Member] | Money market funds [Member]
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total assets measured at fair value 15,275
Level 2 [Member]
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total assets measured at fair value 26,270
Level 2 [Member] | Corporate debt and asset backed securities [Member]
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total assets measured at fair value 26,270
Level 3 [Member]
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total liabilities measured at fair value 8,766
Level 3 [Member] | Warrant liability [Member]
 
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]  
Total liabilities measured at fair value $ 8,766