Stock-Based Compensation Plans - Stock-based Compensation Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 22.4	$ 29.9	$ 42.2	$ 54.0
Continuing operations
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	22.4	21.5	42.2	43.1
Discontinued operations
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0.0	$ 8.4	$ 0.0	$ 10.9