SEGMENT INFORMATION (REVENUE GEOGRAPHY) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 364,936	$ 359,036	$ 1,090,038	$ 1,050,742
Other long-term assets	67,327		67,327		$ 61,857
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	206,433	197,664	605,024	570,305
Philippines [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	85,272	86,938	259,919	258,360
Latin America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	26,351	31,361	84,073	96,301
Europe Middle East Africa [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	16,112	14,892	50,552	45,555
Canada [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	15,400	18,937	47,525	56,035
Asia Pacific India[ Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 15,368	$ 9,244	$ 42,945	$ 24,186