GOODWILL (GOODWILL ROLLFORWARD) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Goodwill [Line Items]
Beginning balance, goodwill	$ 206,694
Effect of Foreign Currency	(1,062)
Ending balance, goodwill	205,632
Customer Management Services [Member]
Goodwill [Line Items]
Beginning balance, goodwill	119,497
Effect of Foreign Currency	(1,161)
Ending balance, goodwill	118,336
Customer Growth Services [Member]
Goodwill [Line Items]
Beginning balance, goodwill	24,439
Ending balance, goodwill	24,439
Customer Technology Services [Member]
Goodwill [Line Items]
Beginning balance, goodwill	40,839
Ending balance, goodwill	40,839
Customer Strategy Services [Member]
Goodwill [Line Items]
Beginning balance, goodwill	21,919
Effect of Foreign Currency	99
Ending balance, goodwill	$ 22,018