ACQUISITIONS - Narrative (Details) $ in Thousands			9 Months Ended
	Nov. 16, 2015 USD ($)	Jul. 10, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)
Business Acquisition [Line Items]
Cash consideration, Deferred			$ 2,260	$ 30,274
NavigationArts
Business Acquisition [Line Items]
Cash consideration, Paid		$ 28,747
Cash Consideration Placed In Escrow		$ 2,670
Consideration Placed In Escrow, Period		18 months
Cash consideration, Deferred			$ 1,797
NavigationArts | Design Consultant
Business Acquisition [Line Items]
Number of professionals		90
AGS
Business Acquisition [Line Items]
Cash consideration, Paid	$ 51,717
Cash Consideration Placed In Escrow	$ 5,000
Consideration Placed In Escrow, Period	15 months
AGS | IT professionals
Business Acquisition [Line Items]
Number of professionals	1,151