GOODWILL AND OTHER INTANGIBLE ASSETS, Amortizable Other Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	$ 169,039	$ 163,149
Accumulated amortization	(89,002)	(84,624)
Carrying amount, net	80,037	78,525
Customer Relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	168,255	162,200
Accumulated amortization	(88,557)	(83,806)
Carrying amount, net	79,698	78,394
Non-Compete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	784	949
Accumulated amortization	(445)	(818)
Carrying amount, net	$ 339	$ 131