SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash paid during the period for:
Interest paid	$ 12,218	$ 3,759	$ 24,387	$ 15,111	$ 36,807	$ 30,850	$ 48,437	$ 42,345	$ 26,070
Income taxes paid (refunds received)	(849)	168	(345)	1,077	584	(33,821)	725	(35,092)	18,106
Non-cash financing and investing activities:
Issuance of seller notes in connection with acquisitions									4,662
Additions to property, plant and equipment acquired through finance obligations	623	162	669	213	1,299	269	1,484	374	3,743
Retirements of financed property, plant and equipment and related financing obligations		1,663	135	2,157	135	2,228	811	2,381	1,434
Purchase of property, plant and equipment in accounts payable	$ 1,337	$ 747	$ 1,100	$ 998	$ 865	$ 1,900	$ 2,119	$ 728	$ 2,746