SEGMENT AND GEOGRAPHICAL REPORTING - Revenues and Property and Equipment by Geographical Location (Details) - USD ($) $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	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, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total revenue	$ 295,500	$ 327,200	$ 333,300	$ 311,200	$ 311,000	$ 308,000	$ 311,200	$ 285,900	$ 265,700	$ 251,900	$ 250,700	$ 238,500	$ 1,267,189	$ 1,216,197	$ 1,006,782
Property and equipment, net	63,703				51,330								63,703	51,330
Reportable Geographical Components | United States
Segment Reporting Information [Line Items]
Total revenue													1,165,000	1,110,000	903,000
Property and equipment, net	56,000				41,000								56,000	41,000
Reportable Geographical Components | Canada
Segment Reporting Information [Line Items]
Total revenue													102,000	106,000	104,000
Property and equipment, net	8,000				10,000								8,000	10,000
Reportable Geographical Components | Other, including Mexico and Dubai
Segment Reporting Information [Line Items]
Total revenue													0	0	$ 0
Reportable Geographical Components | Other, including Dubai
Segment Reporting Information [Line Items]
Property and equipment, net	$ 0				$ 0								$ 0	$ 0