ENTITY WIDE DISCLOSURES - Geographic Breakdown of Revenues and Total Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 312,256	$ 336,440	$ 598,810	$ 587,294
Total assets	1,126,577		1,126,577		$ 1,147,418
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	226,035	241,064	441,247	443,117
Total assets	769,902		769,902		788,780
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	37,444	41,836	64,692	63,821
Total assets	65,989		65,989		66,056
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	30,229	33,152	56,228	50,041
Total assets	235,614		235,614		234,847
Other foreign countries
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	18,548	$ 20,388	36,643	$ 30,315
Total assets	$ 55,072		$ 55,072		$ 57,735