OPERATING SEGMENTS (Revenues by Service Offering) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue from External Customer [Line Items]
Revenues	$ 260,253	$ 236,049	$ 217,781	$ 200,045	$ 202,184	$ 192,764	$ 174,695	$ 160,384	$ 914,128	$ 730,027	$ 555,117
Software development
Revenue from External Customer [Line Items]
Revenues									644,732	504,590	374,426
Application testing services
Revenue from External Customer [Line Items]
Revenues									174,259	140,363	109,222
Application maintenance and support
Revenue from External Customer [Line Items]
Revenues									70,551	58,840	45,971
Infrastructure services
Revenue from External Customer [Line Items]
Revenues									11,311	14,198	14,433
Licensing
Revenue from External Customer [Line Items]
Revenues									3,764	3,626	3,439
Reimbursable expenses and other revenues
Revenue from External Customer [Line Items]
Revenues									$ 9,511	$ 8,410	$ 7,626