SHARE-BASED PAYMENTS - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2021 |
Sep. 30, 2020 |
|
| Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] | ||||
| Stock compensation expense | $ 2,143 | $ 1,826 | $ 6,322 | $ 5,184 |
| Restricted stock units | ||||
| Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] | ||||
| Stock compensation expense | 2,143 | 1,826 | 6,322 | 5,184 |
| Cost of operations | Restricted stock units | ||||
| Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] | ||||
| Stock compensation expense | 1,725 | 1,482 | 5,009 | 3,993 |
| General and administrative | Restricted stock units | ||||
| Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items] | ||||
| Stock compensation expense | $ 418 | $ 344 | $ 1,313 | $ 1,191 |