Stock-Based Compensation - Stock Option Activity (Details) - USD ($)
$ / shares in Units, $ in Thousands |
12 Months Ended |
Dec. 31, 2015 |
Dec. 31, 2014 |
Dec. 31, 2013 |
Dec. 31, 2012 |
| Number of Options |
|
|
|
|
| Outstanding balance at beginning of period (in shares) |
3,425,117
|
2,374,241
|
2,102,985
|
|
| Granted (in shares) |
1,776,150
|
1,690,925
|
528,403
|
|
| Exercised (in shares) |
(543,979)
|
(456,766)
|
(97,248)
|
|
| Cancelled (in shares) |
(359,395)
|
(183,283)
|
(159,899)
|
|
| Outstanding balance at end of period (in shares) |
4,297,893
|
3,425,117
|
2,374,241
|
2,102,985
|
| Exercisable at end of period (in shares) |
1,647,398
|
|
|
|
| Vested and expected to vest at end of period (in shares) |
3,928,026
|
|
|
|
| Weighted- Average Exercise Price |
|
|
|
|
| Outstanding balance at beginning of period (in usd per share) |
$ 7.51
|
$ 2.09
|
$ 1.21
|
|
| Granted (in usd per share) |
6.34
|
13.09
|
5.30
|
|
| Exercised (in usd per share) |
1.44
|
1.45
|
0.73
|
|
| Cancelled (in usd per share) |
9.02
|
3.89
|
1.93
|
|
| Outstanding balance at end of period (in usd per share) |
7.67
|
$ 7.51
|
$ 2.09
|
$ 1.21
|
| Exercisable at end of period (in usd per share) |
6.84
|
|
|
|
| Vested and expected to vest at end of period (in usd per share) |
$ 7.74
|
|
|
|
| Weighted- Average Remaining Contractual Term |
|
|
|
|
| Outstanding balance at end of period (in years) |
8 years 4 months 21 days
|
8 years 4 months 10 days
|
8 years 3 months 4 days
|
8 years 10 months 21 days
|
| Exercisable at end of period (in years) |
7 years 2 months 9 days
|
|
|
|
| Vested and expected to vest at end of period (in years) |
8 years 3 months 15 days
|
|
|
|
| Aggregate Intrinsic Value |
|
|
|
|
| Outstanding balance at end of period |
$ 500
|
$ 26,260
|
$ 17,016
|
$ 4,771
|
| Exercisable at end of period |
497
|
|
|
|
| Vested and expected to vest at end of period |
$ 499
|
|
|
|