DERIVATIVES - Schedule of Activity of Foreign Currency Contracts (Details) - Foreign currency contracts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Unrealized gain, net of less than $0.1 million and $0.2 million income tax, included in “Accumulated items of other comprehensive loss” in the accompanying consolidated balance sheets	$ 145	$ 600
Realized loss on effective portion, included as compensation expense primarily in “Direct costs of customer support” and “Sales, general and administrative” in the accompanying consolidated statements of operations and comprehensive loss	(171)	328
Cash Flow Hedging | Designated as Hedging Instrument
Derivative [Line Items]
Tax on unrealized gain arising from foreign currency contracts	$ 100	$ 200