STOCK-BASED COMPENSATION (Costs Related to Stock Compensation Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 72,036	$ 59,188	$ 52,407
Cost of Revenues (Exclusive of Depreciation and Amortization)
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	37,580	27,245	20,868
Selling, General and Administrative Expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	34,456	$ 31,943	$ 31,539
Year 2020 | 2019 Acquisitions
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 348