Net Income Per Common Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Basic Net Income Per Common Share
Average Number of Common Shares Outstanding (in shares)	195,192,789	204,628,796
Net Income	$ 392.0	$ 214.7
Less: Dividends on Preferred Stock	16.2	16.2
Net Income Applicable to Common Stock	375.8	198.5
Less: Earnings Allocated to Participating Securities	3.6	2.4
Earnings Allocated to Common Shares Outstanding	$ 372.2	$ 196.1
Basic Net Income Per Common Share (in dollars per share)	$ 1.91	$ 0.96
Diluted Net Income Per Common Share
Average Number of Common Shares Outstanding (in shares)	195,192,789	204,628,796
Plus: Dilutive Effect of Share-based Compensation (in shares)	932,182	506,049
Average Common and Potential Common Shares (in shares)	196,124,971	205,134,845
Earnings Allocated to Common and Potential Common Shares	$ 372.2	$ 196.1
Diluted Net Income Per Common Share (in dollars per share)	$ 1.90	$ 0.96
Common stock equivalents excluded from the computation of diluted earnings per share because their inclusion would have been antidilutive (in shares)	0	0