REVENUE - Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Movement in Deferred Revenue [Roll Forward]
Deferred revenue, beginning of the period	$ 59,501	$ 51,549	$ 51,804	$ 44,331
Deferred revenue, end of the period	58,684	53,166	58,684	53,166
Deferred revenue arising from business combination	1,068	800	6,448	800
Revenue recognized in the period from amounts included in deferred revenue at the beginning of the period	$ 25,867	$ 17,560	$ 40,293	$ 33,885