Stock-Based Compensation (Details) - Stock-Based Compensation Expense Recognized In Consolidated Statements Of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 78.9	$ 46.7	$ 46.1
Cost of services and product development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	25.8	21.9	20.6
Selling, general and administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	35.5	24.8	25.5
Acquisition and integration charges
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 17.6	$ 0.0	$ 0.0