Non-vested Award Activity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Stock-settled awards
Stock-based Payment Award
Non-vested as of January 1, 2018	2.9
Nonvested as of January 1, 2018, weighted-average grant date fair value	$ 34.20
Granted	1.4
Granted, Weighted-average grant-date fair value	$ 31.39	$ 35.54	$ 36.36
Vested	(0.6)
Vested, Weighted-average grant date fair value	$ 27.82
Forfeited	(0.4)
Forfeited, Weighted-average grant date fair value	$ 35.42
Non-vested as of December 31, 2018	3.3	2.9
Nonvested as of December 31, 2018, weighted-average grant date fair value	$ 34.08	$ 34.20
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Reinstated in Period, Weighted Average Grant Date Fair Value	$ 36.31
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Other	0.0
Total unrecognized compensation expense remaining	$ 45.8
Weighted-average years expected to be recognized over	1 year 3 months 18 days
Cash-settled awards
Stock-based Payment Award
Non-vested as of January 1, 2018	0.0
Nonvested as of January 1, 2018, weighted-average grant date fair value	$ 36.05
Granted	0.1
Granted, Weighted-average grant-date fair value	$ 31.40	$ 35.71	$ 36.53
Vested	(0.0)
Vested, Weighted-average grant date fair value	$ 0.0
Forfeited	(0.0)
Forfeited, Weighted-average grant date fair value	$ 32.21
Non-vested as of December 31, 2018	0.1	0.0
Nonvested as of December 31, 2018, weighted-average grant date fair value	$ 32.64	$ 36.05
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Reinstated in Period, Weighted Average Grant Date Fair Value	$ 0.0
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Other	0.0
Total unrecognized compensation expense remaining	$ 1.9
Weighted-average years expected to be recognized over	1 year 8 months 12 days
Cash awards granted during the period target value	$ 17.1	$ 20.4	$ 19.9
Incentive compensation expense, non share-based	$ 16.7	$ 31.5	$ 42.0
Performance-based awards
Stock-based Payment Award
Non-vested as of January 1, 2018	2.3
Nonvested as of January 1, 2018, weighted-average grant date fair value	$ 32.09
Granted	2.8
Granted, Weighted-average grant-date fair value	$ 27.53	$ 26.31	$ 29.95
Vested	(0.3)
Vested, Weighted-average grant date fair value	$ 23.38
Forfeited	(0.5)
Forfeited, Weighted-average grant date fair value	$ 31.39
Non-vested as of December 31, 2018	4.4	2.3
Nonvested as of December 31, 2018, weighted-average grant date fair value	$ 29.86	$ 32.09
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Reinstated in Period, Weighted Average Grant Date Fair Value	$ 32.96
Share-Based Compensation Arrangement by Share-Based Payment Award, Non-Option Equity Instruments, Other	0.1
Total unrecognized compensation expense remaining	$ 44.9
Weighted-average years expected to be recognized over	1 year 10 months 24 days
Cash awards granted during the period target value	$ 1.5	$ 46.2	$ 46.0
Incentive compensation expense, non share-based	$ 19.5	$ 38.0	$ 44.7