OPERATING SEGMENTS - Revenue and Long-lived 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
Revenue and Long-Lived Assets Outside of the United States
Total revenue	$ 134,054	$ 124,824	$ 370,345	$ 360,493
Total long- lived assets	459,610		459,610		$ 460,593
United States
Revenue and Long-Lived Assets Outside of the United States
Total revenue	112,821	111,005	319,776	325,379
Total long- lived assets	400,269		400,269		405,767
Canada
Revenue and Long-Lived Assets Outside of the United States
Total revenue	21,233	$ 13,819	50,569	$ 35,114
Total long- lived assets	$ 59,341		$ 59,341		$ 54,826