SEGMENT AND GEOGRAPHIC DISCLOSURES - Geographic Breakdown of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Revenues from External Customers [Line Items]
Revenues	$ 315,829	$ 343,889	$ 585,428	$ 646,274
United States
Revenues from External Customers [Line Items]
Revenues	230,563	242,773	436,671	476,149
Canada
Revenues from External Customers [Line Items]
Revenues	35,330	51,164	54,651	78,532
Europe
Revenues from External Customers [Line Items]
Revenues	34,882	32,471	63,378	60,696
Other foreign countries
Revenues from External Customers [Line Items]
Revenues	$ 15,054	$ 17,481	$ 30,728	$ 30,897