REVENUE RECOGNITION - Summary of Contract Assets and Contract Liabilities from Contracts with Customers (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Receivables	$ 97,537	$ 78,938
Short-term contract assets (Prepaid expenses and other assets)	13,900	13,516
Long-term contract assets (Other assets)	36,418	34,148
Short-term contract liabilities (Deferred revenues)	33,577	33,119
Long-term contract liabilities (Deferred revenues)	$ 82,288	$ 76,911