Capitalization and Warrant Liability - Common Stock Shares Reserved for Future Issuance (Detail) - shares
|
Dec. 31, 2016 |
Dec. 31, 2015 |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Common Stock Shares Reserved For Future Issuance |
19,834,145
|
13,703,058
|
| Stock-Based Compensation Plans [Member] |
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Common Stock Shares Reserved For Future Issuance |
17,940,618
|
8,838,165
|
| Warrants to Purchase Common Stock 2011 Offering [Member] |
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Common Stock Shares Reserved For Future Issuance |
|
1,310,000
|
| Warrants to Purchase Common Stock 2012 Offering [Member] |
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Common Stock Shares Reserved For Future Issuance |
1,893,527
|
2,054,893
|
| Warrants to Purchase Common Stock 2014 Offering [Member] |
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |
|
|
| Common Stock Shares Reserved For Future Issuance |
|
1,500,000
|