ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (INCOME STATEMENT CLASSIFICATION TABLE) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Presentation of Income Statement Reclassifications [Line Items]
Sales Revenue Services Net	$ 392,515	$ 349,853	$ 786,871	$ 725,102
Interest Expense.	4,208	7,765	9,496	14,224
Benefit from (provision for) income taxes	(7,345)	(653)	(14,811)	(2,755)
Net income	13,614	6,297	34,090	12,229
Accumulated Other Comprehensive Income (Loss)
Presentation of Income Statement Reclassifications [Line Items]
Net Income (Loss) - Other			2,682	7,659
Derivative Valuation, Net of Tax
Presentation of Income Statement Reclassifications [Line Items]
Net Income (Loss) - Other			2,583	7,458
Tax effect
Presentation of Income Statement Reclassifications [Line Items]
Provision for income taxes - Other	6	11	11	22
Reclassification from accumulated other comprehensive income
Presentation of Income Statement Reclassifications [Line Items]
Cost of services	(55)	(112)	(110)	(223)
Net Income (Loss) - Other	(49)	(101)	(99)	(201)
Reclassification from accumulated other comprehensive income | Foreign Currency Translation Adjustment
Presentation of Income Statement Reclassifications [Line Items]
Sales Revenue Services Net	(1,011)	(4,883)	(3,538)	(10,215)
Reclassification from accumulated other comprehensive income | Derivative Valuation, Net of Tax
Presentation of Income Statement Reclassifications [Line Items]
Net income	(738)	(3,565)	(2,583)	(7,458)
Reclassification from accumulated other comprehensive income | Tax effect
Presentation of Income Statement Reclassifications [Line Items]
Benefit from (provision for) income taxes	$ 273	$ 1,318	$ 955	$ 2,757