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Assumptions Used to Estimate Warrant Values (Detail) (Warrant, USD $)
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0 Months Ended | 12 Months Ended | 0 Months Ended | 12 Months Ended |
|---|---|---|---|---|
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Jun. 03, 2013
First Issuance
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Dec. 31, 2013
First Issuance
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Nov. 15, 2013
Second Issuance
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Dec. 31, 2013
Second Issuance
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| Class of Warrant or Right [Line Items] | ||||
| Class A Common Stock: Closing Market Price | $ 2.94 | $ 3.02 | $ 3.21 | $ 3.02 |
| Market Price Volatility | 102.93% | 95.00% | 95.00% | 95.00% |
| Expected average term of warrants, in years | 5 years | 4 years 6 months | 5 years 6 months | 5 years 6 months |
| Expected dividend yield | 0.00% | 0.00% | 0.00% | 0.00% |