REVENUE AND CONTRACT LIABILITY - Deferred Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Unearned revenue, beginning balance	$ 41,821	$ 50,578
Increase (Decrease) in Contract with Customer, Liability	65,828	36,622
Contract with Customer, Liability, Revenue Recognized	(35,338)	(45,379)
Unearned revenue, ending balance	$ 72,311	$ 41,821