SUPPLEMENTAL CASH FLOW INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		9 Months Ended		12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash paid during the period for:
Interest	$ 2,537	$ 4,221	$ 12,344	$ 16,314	$ 15,283	$ 19,144	$ 25,341	$ 28,938	$ 31,122
Income taxes	11,159	5,591	11,538	15,558	19,095	21,033	25,433	34,409	34,468
Non-cash financing and investing activities:
Issuance of seller notes in connection with acquisitions	8,450		11,901	268	13,172	614	13,964	2,344	20,223
Issuance of note in connection with intangible acquisition									500
Additions to property, plant and equipment acquired through financing obligations	1,266	386	1,973	740	3,001	2,797	3,461	3,958	3,094
Retirements of financed property, plant and equipment and related financing obligations	7		7	150	2,097	529	2,071	399	2,095
Purchase of property, plant and equipment in accounts payable	$ 2,184	$ 357	$ 1,169	$ 574	$ 1,793	$ 638	$ 1,588	$ 1,109	$ 416