Stock-Based Compensation Plans - Stock-based Compensation Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 51.9	$ 78.9	$ 98.1
Continuing Operations
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	51.9	78.9	87.2
Discontinued Operations
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0.0	$ 0.0	$ 10.9