GOODWILL AND OTHER INTANGIBLE ASSETS - Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 1,017	$ 2,835	$ 5,608	$ 8,508
Cost of revenue
Acquired Finite-Lived Intangible Assets [Line Items]
Total amortization expense	647	1,232	2,854	3,695
Selling and marketing
Acquired Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 370	$ 1,603	$ 2,754	$ 4,813