SEGMENT AND GEOGRAPHIC INFORMATION (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEGMENT AND GEOGRAPHIC INFORMATION
Revenue									$ 518,920	$ 519,289	$ 521,100
Long-lived assets:	$ 186,101				$ 178,972				186,101	178,972	180,905
United States
SEGMENT AND GEOGRAPHIC INFORMATION
Long-lived assets:	151,770				145,210				151,770	145,210	147,296
Canada
SEGMENT AND GEOGRAPHIC INFORMATION
Long-lived assets:	31,843				30,823				31,843	30,823	29,806
Mexico and Other
SEGMENT AND GEOGRAPHIC INFORMATION
Long-lived assets:	2,488				2,939				2,488	2,939	3,803
Product
SEGMENT AND GEOGRAPHIC INFORMATION
Revenue	$ 127,264	$ 181,505	$ 105,623	$ 100,859	$ 125,179	$ 182,173	$ 104,897	$ 103,425	515,251	515,674	517,373
Product | United States
SEGMENT AND GEOGRAPHIC INFORMATION
Revenue									471,561	472,222	475,055
Product | Canada, Mexico, and Other
SEGMENT AND GEOGRAPHIC INFORMATION
Revenue									43,690	43,452	42,318
Rental and Royalty
SEGMENT AND GEOGRAPHIC INFORMATION
Revenue									$ 3,669	$ 3,615	$ 3,727