SHARE-BASED COMPENSATION - RSUs with Market Conditions (Details) - USD ($) $ / shares in Units, $ in Thousands |
6 Months Ended | 12 Months Ended |
|---|---|---|
Jun. 30, 2018 |
Dec. 31, 2017 |
|
| Share-based Compensation Restricted Stock Units With Market Conditions [Line Items] | ||
| RSUs issued | 1,279,660 | |
| Reconciliation Of RSUs With Market Conditions [Abstract] | ||
| RSUs beginning | 4,285,290 | |
| Number of RSUs granted | 1,279,660 | |
| Number of RSUs forfeited | (238,606) | |
| Number of RSUs vested | (1,485,340) | |
| RSUs ending | 3,841,004 | 4,285,290 |
| Net RSUs increase (decrease) to APIC | $ 7,653 | $ 9,567 |
| Restricted Stock Units With Market Conditions [Member] | ||
| Share-based Compensation Restricted Stock Units With Market Conditions [Line Items] | ||
| RSUs issued | 0 | 70,000 |
| Reconciliation Of RSUs With Market Conditions [Abstract] | ||
| RSUs beginning | 650,000 | 630,000 |
| Number of RSUs granted | 0 | 70,000 |
| Number of RSUs forfeited | (110,000) | 0 |
| Number of RSUs vested | (314,000) | (50,000) |
| RSUs ending | 226,000 | 650,000 |
| Fair value of each RSU issued with market conditions | $ 0 | $ 9.81 |