STOCK BASED COMPENSATION - Nonvested stock option (Details) - Stock option - $ / shares |
12 Months Ended | |
|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
|
| Number of shares | ||
| Nonvested at December 31, 2015 (in shares) | 565,798 | |
| Granted (in shares) | 182,118 | 176,093 |
| Vested (in shares) | (132,184) | |
| Forfeited (in shares) | (25,956) | |
| Nonvested at December 31, 2016 (in shares) | 589,776 | 565,798 |
| Weighted average grant date fair value | ||
| Nonvested at December 31, 2015 (in dollars per shares) | $ 2.61 | |
| Granted (in dollars per shares) | 2.94 | |
| Vested (in dollars per shares) | 2.41 | |
| Forfeited (in dollars per shares) | 2.18 | |
| Nonvested at December 31, 2016 (in dollars per shares) | $ 2.73 | $ 2.61 |