ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (INCOME STATEMENT CLASSIFICATION TABLE) (DETAILS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Presentation of Income Statement Reclassifications [Line Items]
Sales Revenue Services Net	$ 359,036	$ 312,796	$ 1,050,742	$ 930,311
Interest Expense.	3,469	2,041	8,699	5,758
Benefit from (provision for) income taxes	(2,071)	813	(9,059)	(6,667)
Net income	15,575	12,649	51,536	37,096
Accumulated Other Comprehensive Income (Loss)
Presentation of Income Statement Reclassifications [Line Items]
Net Income (Loss) - Other			11,046	12,317
Derivative Valuation, Net of Tax
Presentation of Income Statement Reclassifications [Line Items]
Net Income (Loss) - Other			10,694	11,189
Reclassification from accumulated other comprehensive income
Presentation of Income Statement Reclassifications [Line Items]
Net income			(10,694)	(11,189)
Cost of services	(130)	(804)	(391)	(1,252)
Net Income (Loss) - Other	(117)	(724)	(352)	(1,128)
Reclassification from accumulated other comprehensive income | Derivative Valuation, Net of Tax
Presentation of Income Statement Reclassifications [Line Items]
Net income	(3,487)	(4,179)
Reclassification from accumulated other comprehensive income | Tax effect
Presentation of Income Statement Reclassifications [Line Items]
Benefit from (provision for) income taxes	2,325	3,028	7,130	8,106
Provision for income taxes - Other	13	80	39	124
Foreign Exchange Forward | Reclassification from accumulated other comprehensive income
Presentation of Income Statement Reclassifications [Line Items]
Sales Revenue Services Net	$ (5,812)	(7,103)	(17,709)	(18,860)
Interest Rate | Reclassification from accumulated other comprehensive income | Loss on interest rate swaps [Member]
Presentation of Income Statement Reclassifications [Line Items]
Interest Expense.		$ (104)	$ (115)	$ (435)