GOODWILL AND INTANGIBLE ASSETS - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Intangible assets	$ 610,900	$ 615,086
Accumulated amortization	(317,589)	(256,025)
Intangible assets, net	293,311	359,061
Amortization expense	65,700	66,400	$ 68,100
Future amortization expense
2019	64,900
2020	65,100
2021	52,000
2022	24,500
2023	13,400
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Intangible assets	229,300	231,620
Accumulated amortization	(106,761)	(96,147)
Intangible assets, net	122,539	135,473
Customer contracts
Finite-Lived Intangible Assets [Line Items]
Intangible assets	381,600	383,466
Accumulated amortization	(210,828)	(159,878)
Intangible assets, net	$ 170,772	$ 223,588