Fair Value of Warrants - Additional Information (Detail) - $ / shares |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
|---|---|---|---|
| Class of Warrant or Right [Line Items] | |||
| Fair value of warrants issue price (USD per share) | $ 3.30 | $ 6.68 | |
| Minimum | |||
| Class of Warrant or Right [Line Items] | |||
| Fair value of stock prices in computing fair value for warrants issued (USD per share) | 3.30 | 6.68 | $ 9.6 |
| Maximum | |||
| Class of Warrant or Right [Line Items] | |||
| Fair value of stock prices in computing fair value for warrants issued (USD per share) | $ 11.76 | $ 19.86 | $ 20.26 |