ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (INCOME STATEMENT CLASSIFICATION TABLE) (DETAILS) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Presentation of Income Statement Reclassifications [Line Items]
Sales Revenue Services Net	$ 338,277	$ 312,410
Interest Expense.	2,318	1,964
Benefit from (provision for) income taxes	(5,391)	(4,528)
Net income	20,167	11,905
Accumulated Other Comprehensive Income (Loss)
Presentation of Income Statement Reclassifications [Line Items]
Net Income (Loss) - Other	4,253	3,755
Derivative Valuation, Net of Tax
Presentation of Income Statement Reclassifications [Line Items]
Net Income (Loss) - Other	4,136	3,553
Reclassification from accumulated other comprehensive income
Presentation of Income Statement Reclassifications [Line Items]
Net income	(4,136)	(3,553)
Net Income (Loss) - Other	(117)	(202)
Reclassification from accumulated other comprehensive income | Tax effect
Presentation of Income Statement Reclassifications [Line Items]
Benefit from (provision for) income taxes	2,759	2,573
Provision for income taxes - Other	13	22
Reclassification from accumulated other comprehensive income | Cost of Services
Presentation of Income Statement Reclassifications [Line Items]
Cost of services	(130)	(224)
Foreign Exchange Forward | Reclassification from accumulated other comprehensive income | Foreign Currency Translation Adjustment
Presentation of Income Statement Reclassifications [Line Items]
Sales Revenue Services Net	(6,806)	(5,897)
Interest Rate | Reclassification from accumulated other comprehensive income | Loss on interest rate swaps [Member]
Presentation of Income Statement Reclassifications [Line Items]
Interest Expense.	$ (89)	$ (229)