DERIVATIVES (INCOME STATEMENT CLASSIFICATION) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Sales Revenue Services Net	$ 461,326	$ 395,507	$ 392,515	$ 394,356	$ 419,133	$ 364,936	$ 349,853	$ 375,249	$ 1,643,704	$ 1,509,171	$ 1,477,365
Other nonoperating income expense									3,902	(11,618)	$ 1,869
Designated as Hedging Instruments [Member] | Foreign Exchange [Member] | Cash Flow [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) recognized in other comprehensive income (loss) - effective portion, net of tax:									(3,085)	(12,810)
Designated as Hedging Instruments [Member] | Foreign Exchange [Member] | Cash Flow [Member] | Reclassification from accumulated other comprehensive income | Revenue
Derivative Instruments, Gain (Loss) [Line Items]
Sales Revenue Services Net									(4,228)	(17,548)
Not Designated as Hedging Instruments [Member] | Foreign Exchange [Member] | Fair Value [Member] | Other income (expense), net
Derivative Instruments, Gain (Loss) [Line Items]
Other nonoperating income expense									$ 1,773	$ (7,436)