BUSINESS, PRESENTATION, AND RECENT ACCOUNTING PRONOUNCEMENTS - Geographic (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) segment	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Number of segments | segment	1
Revenue recognition	$ 54,521	$ 49,774
Property and equipment, net	40,767		$ 41,269
United States [Member]
Revenue recognition	53,327	48,231
Property and equipment, net	26,612		26,960
Canada [Member]
Revenue recognition	1,194	$ 1,543
Property and equipment, net	$ 14,155		$ 14,309