BUSINESS, PRESENTATION, AND RECENT ACCOUNTING PRONOUNCEMENTS - Geographic (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) segment	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Number of segments | segment			1
Revenue recognition	$ 48,625	$ 48,470	$ 103,146	$ 98,244
Property and equipment, net	40,334		40,334		$ 41,269
United States [Member]
Revenue recognition	47,580	46,277	100,907	94,508
Property and equipment, net	26,252		26,252		26,960
Canada [Member]
Revenue recognition	1,045	$ 2,193	2,239	$ 3,736
Property and equipment, net	$ 14,082		$ 14,082		$ 14,309