GOODWILL AND OTHER INTANGIBLE ASSETS - Amortization of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 1,656	$ 2,836	$ 4,592	$ 5,673
Cost of revenue
Acquired Finite-Lived Intangible Assets [Line Items]
Total amortization expense	875	1,231	2,207	2,463
Selling and marketing
Acquired Finite-Lived Intangible Assets [Line Items]
Total amortization expense	$ 781	$ 1,605	$ 2,385	$ 3,210