ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (INCOME STATEMENT CLASSIFICATION TABLE) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Presentation of Income Statement Reclassifications [Line Items]
Sales Revenue Services Net	$ 395,507	$ 364,936	$ 1,182,378	$ 1,090,038
Interest Expense.	4,041	8,410	13,537	22,634
Benefit from (provision for) income taxes	(5,196)	(1,893)	(20,007)	(4,648)
Net income	19,979	6,744	54,069	18,973
Accumulated Other Comprehensive Income (Loss)
Presentation of Income Statement Reclassifications [Line Items]
Net Income (Loss) - Other			3,523	10,742
Derivative Valuation, Net of Tax
Presentation of Income Statement Reclassifications [Line Items]
Net Income (Loss) - Other			3,376	10,439
Tax effect
Presentation of Income Statement Reclassifications [Line Items]
Provision for income taxes - Other	6	11	18	32
Reclassification from accumulated other comprehensive income
Presentation of Income Statement Reclassifications [Line Items]
Cost of services	(55)	(112)	(165)	(335)
Net Income (Loss) - Other	(49)	(101)	(147)	(303)
Reclassification from accumulated other comprehensive income | Foreign Currency Translation Adjustment
Presentation of Income Statement Reclassifications [Line Items]
Sales Revenue Services Net	(1,087)	(4,085)	(4,625)	(14,300)
Reclassification from accumulated other comprehensive income | Derivative Valuation, Net of Tax
Presentation of Income Statement Reclassifications [Line Items]
Net income	(793)	(2,981)	(3,376)	(10,439)
Reclassification from accumulated other comprehensive income | Tax effect
Presentation of Income Statement Reclassifications [Line Items]
Benefit from (provision for) income taxes	$ 294	$ 1,104	$ 1,249	$ 3,861