Stock Option Plans -Summary of Stock Option Activity for Employee and Nonemployee Awards under Plan (Detail) - USD ($)
$ / shares in Units, $ in Thousands |
12 Months Ended |
Dec. 31, 2015 |
Dec. 31, 2014 |
| Number of shares |
|
|
| Number of Shares, Outstanding |
2,126,176
|
|
| Number of Shares, Granted |
2,360,682
|
|
| Number of Shares, Exercised |
(370,230)
|
|
| Number of Shares, Forfeited |
(661,702)
|
|
| Number of Shares, Outstanding |
3,454,926
|
2,126,176
|
| Number of Shares, Options expected to vest |
2,336,878
|
|
| Number of Shares, Options exercisable |
1,001,415
|
|
| Weighted-Average Exercise Price |
|
|
| Weighted-Average Exercise Price, Outstanding |
$ 4.97
|
|
| Weighted-Average Exercise Price, Granted |
5.66
|
|
| Weighted-Average Exercise Price, Exercised |
4.40
|
|
| Weighted-Average Exercise Price, Forfeited |
5.86
|
|
| Weighted-Average Exercise Price, Outstanding |
5.39
|
$ 4.97
|
| Weighted-Average Exercise Price, Options expected to vest |
5.32
|
|
| Weighted-Average Exercise Price, Options exercisable |
$ 5.56
|
|
| Weighted-Average Remaining Contractual Life (Years) |
|
|
| Weighted-Average Remaining Contractual Life (Years) |
8 years 10 months 24 days
|
6 years 8 months 12 days
|
| Weighted-Average Remaining Contractual Life (Years), Options expected to vest - December 31, 2014 |
9 years 4 months 24 days
|
|
| Weighted-Average Remaining Contractual Life (Years), Options exercisable - December 31, 2014 |
7 years 8 months 12 days
|
|
| Aggregate Intrinsic Value |
|
|
| Aggregate Intrinsic Value, Outstanding |
|
$ 2,701
|