INCOME TAXES - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] | |||
| Gross unrecognized tax benefit - beginning balance | $ 3,316 | $ 2,539 | $ 1,797 |
| Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions | (21) | 0 | 0 |
| Increases related to tax positions taken during current year | 1,146 | 777 | 742 |
| Gross unrecognized tax benefit - ending balance | $ 4,441 | $ 3,316 | $ 2,539 |