STOCK-BASED COMPENSATION (Total Stock-Based Compensation Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense, before income taxes	$ 37.1	$ 38.4	$ 38.1
Cost of services
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense, before income taxes	4.5	5.0	4.6
Selling, general and administrative expenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense, before income taxes	$ 32.6	$ 33.4	$ 33.5