BUSINESS, PRESENTATION, AND RECENT ACCOUNTING PRONOUNCEMENTS - Geographic (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Number of segments | segment			1
Revenue recognition	$ 52,061	$ 52,979	$ 155,207	$ 151,223
Property and equipment, net	39,526		39,526		$ 41,269
United States [Member]
Revenue recognition	51,100	52,094	152,007	146,602
Property and equipment, net	25,512		25,512		26,960
Canada [Member]
Revenue recognition	961	$ 885	3,200	$ 4,621
Property and equipment, net	$ 14,014		$ 14,014		$ 14,309