GOODWILL AND OTHER INTANGIBLE ASSETS - Amortization Expense of Acquired Intangibles (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 6,625	$ 11,443	$ 12,338
Cost of revenue
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	3,500	5,027	5,103
Selling and marketing
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 3,125	$ 6,416	$ 7,235