ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (INCOME STATEMENT CLASSIFICATION TABLE) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Presentation of Income Statement Reclassifications [Line Items]
Revenues	$ 364,936	$ 359,036	$ 1,090,038	$ 1,050,742
Interest Expense.	8,410	3,469	22,634	8,699
Benefit from (provision for) income taxes	(1,893)	(2,071)	(4,648)	(9,059)
Net income	6,744	15,575	18,973	51,536
Accumulated Other Comprehensive Income (Loss)
Presentation of Income Statement Reclassifications [Line Items]
Net Income (Loss) - Other			10,742	11,046
Derivative Valuation, Net of Tax
Presentation of Income Statement Reclassifications [Line Items]
Net Income (Loss) - Other			10,439	10,694
Loss on interest rate swaps [Member]
Presentation of Income Statement Reclassifications [Line Items]
Interest Expense.				(115)
Tax effect
Presentation of Income Statement Reclassifications [Line Items]
Provision for income taxes - Other	11	13	(32)	(39)
Reclassification from accumulated other comprehensive income
Presentation of Income Statement Reclassifications [Line Items]
Net income			(10,439)	(10,694)
Cost of services	(112)	(130)	(335)	(391)
Net Income (Loss) - Other	(101)	(117)	(303)	(352)
Reclassification from accumulated other comprehensive income | Foreign Currency Translation Adjustment
Presentation of Income Statement Reclassifications [Line Items]
Revenues	(4,085)	(5,812)
Reclassification from accumulated other comprehensive income | Derivative Valuation, Net of Tax
Presentation of Income Statement Reclassifications [Line Items]
Net income	(2,981)	(3,487)
Reclassification from accumulated other comprehensive income | Tax effect
Presentation of Income Statement Reclassifications [Line Items]
Benefit from (provision for) income taxes	$ 1,104	$ 2,325	3,861	7,130
Foreign Exchange Forward | Foreign Currency Translation Adjustment
Presentation of Income Statement Reclassifications [Line Items]
Revenues			$ (14,300)	$ (17,709)