STOCK BASED COMPENSATION - Summary of Stock Option Activity (Details) - Stock options - USD ($)
$ / shares in Units, $ in Thousands |
12 Months Ended |
Dec. 31, 2016 |
Dec. 31, 2015 |
| Stock option activity |
|
|
| Outstanding at beginning of year (in shares) |
1,452,149
|
|
| Granted (in shares) |
1,063,981
|
|
| Exercised (in shares) |
(81,831)
|
|
| Cancelled (in shares) |
(107,498)
|
|
| Outstanding at end of period (in shares) |
2,326,801
|
1,452,149
|
| Exercisable at end of period (in shares) |
556,040
|
|
| Vested and expected to vest at end of period (in shares) |
2,291,971
|
|
| Weighted average exercise price per share |
|
|
| Outstanding at beginning of year (in dollars per share) |
$ 10.37
|
|
| Granted (in dollars per share) |
16.46
|
|
| Exercised (in dollars per share) |
5.41
|
|
| Cancelled (in dollars per share) |
16.05
|
|
| Outstanding at end of period (in dollars per share) |
13.07
|
$ 10.37
|
| Exercisable at end of period (in dollars per share) |
9.19
|
|
| Vested and expected to vest at end of period (in dollars per share) |
$ 13.11
|
|
| Stock option activity, additional information |
|
|
| Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value |
$ 952
|
|
| Outstanding Weighted-average remaining contractual term |
8 years 8 months 12 days
|
10 years 4 months 24 days
|
| Exercisable at end of period, Weighted-average remaining contractual term |
8 years
|
|
| Vested and expected to vest at end of period, Weighted-average remaining contractual term |
8 years 8 months 12 days
|
|
| Outstanding Aggregate Intrinsic Value |
$ 7,927
|
$ 24,887
|
| Exercisable at end of period, Aggregate Intrinsic Value |
3,917
|
|
| Vested and expected to vest at end of period, Aggregate Intrinsic Value |
8,090
|
|
| Unrecognized compensation cost related to outstanding options |
$ 14,499
|
|
| Period over which unrecognized compensation cost is expected to be recognized as expense |
2 years 9 months 18 days
|
|
| Weighted average fair value of vested options (in dollars per share) |
$ 6.35
|
|
| Weighted-average grant date fair value per share of employee option grants (in dollars per share) |
$ 10.98
|
|