STOCK-BASED COMPENSATION (Costs Related to Stock Compensation Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 59,188	$ 52,407	$ 49,244
Cost of Revenues (Exclusive of Depreciation and Amortization)
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	27,245	20,868	16,619
Selling, General and Administrative Expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 31,943	$ 31,539	$ 32,625