REVENUE - Deferred Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Movement in Deferred Revenue [Roll Forward]
Deferred revenue, beginning of the period	$ 44,331	$ 36,451
Deferred revenue, end of the period	47,046	42,160
Revenue recognized in the period from amounts included in deferred revenue at the beginning of the period	$ 15,570	$ 12,306