SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Disaggregate revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Partner and Marketplace	$ 2,610	$ 2,387
Enterprise	3,178	1,874
Total revenues	$ 5,788	$ 4,261