Stock-Based Compensation - Stock-based Compensation Expense by Award Type and Expense Category (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 43.0	$ 39.7	$ 93.2	$ 90.2
Cost of services and product development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	16.9	15.3	37.5	34.8
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	26.1	24.4	55.7	55.4
Stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	4.0	3.0	7.4	7.6
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	38.7	36.4	85.3	82.0
Common stock equivalents
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	0.3	0.3	0.5	0.6
Retirement Eligible Employees Equity Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 19.0	$ 18.4	$ 47.0	$ 49.0