INTANGIBLE ASSETS - Summary of Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 214,061	$ 213,816
Accumulated Amortization	(107,459)	(96,797)
Net Carrying Amount	106,602	117,019
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	175,091	174,940
Accumulated Amortization	(73,125)	(63,727)
Net Carrying Amount	101,966	111,213
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,466	5,466
Accumulated Amortization	(5,466)	(5,306)
Net Carrying Amount	0	160
Trade names
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	24,792	24,724
Accumulated Amortization	(21,604)	(21,146)
Net Carrying Amount	3,188	3,578
Technology
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	7,858	7,838
Accumulated Amortization	(6,567)	(5,976)
Net Carrying Amount	1,291	1,862
Licenses
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	854	848
Accumulated Amortization	(697)	(642)
Net Carrying Amount	$ 157	$ 206