BUSINESS COMBINATIONS - Restructuring charges (Details) - USD ($) $ in Thousands |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
Jun. 30, 2019 |
Jun. 30, 2018 |
|
| Restructuring Cost and Reserve [Line Items] | ||||
| Total restructuring charges | $ 3,362 | $ 686 | $ 4,376 | $ 2,167 |
| Costs to exit duplicative contracts [Member] | ||||
| Restructuring Cost and Reserve [Line Items] | ||||
| Total restructuring charges | 0 | 349 | 0 | 510 |
| Workforce reduction [Member] | ||||
| Restructuring Cost and Reserve [Line Items] | ||||
| Total restructuring charges | 3,100 | 337 | 3,793 | 928 |
| Lease abandonment costs [Member] | ||||
| Restructuring Cost and Reserve [Line Items] | ||||
| Total restructuring charges | 0 | 257 | ||
| Other restructuring costs [Member] | ||||
| Restructuring Cost and Reserve [Line Items] | ||||
| Total restructuring charges | $ 262 | $ 0 | $ 583 | $ 472 |