RECEIVABLES, CONTRACT ASSETS, AND DEFERRED REVENUE - Summary of Contract Assets and Deferred Revenue (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Receivables [Abstract]
Contract assets	$ 8,104	$ 5,558
Long-term contract assets	5,579	5,420
Total contract assets	13,683	10,978
Deferred revenue	181,680	190,080
Long-term deferred revenue	6,673	5,407
Total deferred revenue	$ 188,353	$ 195,487