GOODWILL AND INTANGIBLE ASSETS - Estimated Useful Lives of Finite-Lived Intangible Assets (Details)	6 Months Ended
	Jun. 30, 2019
Customer relationships | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, estimated useful life	5 years
Customer relationships | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, estimated useful life	16 years
Trade names | Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, estimated useful life	3 years
Trade names | Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, estimated useful life	20 years
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible asset, estimated useful life	3 years