ENTITY WIDE DISCLOSURES - Geographic Breakdown of Revenues and Total Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 285,067	$ 289,577	$ 883,877	$ 876,871
Total assets	1,047,490		1,047,490		$ 1,147,418
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	204,224	208,009	645,471	651,126
Total assets	688,287		688,287		788,780
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	32,939	33,747	97,631	97,568
Total assets	62,664		62,664		66,056
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	30,515	27,930	86,743	77,971
Total assets	240,646		240,646		234,847
Other foreign countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	17,389	$ 19,891	54,032	$ 50,206
Total assets	$ 55,893		$ 55,893		$ 57,735