Net Income Per Common Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Basic Net Income Per Common Share
Average Number of Common Shares Outstanding (in shares)	185,499,213	195,192,789
Net Income	$ 525.5	$ 392.0
Less: Dividends on Preferred Stock	16.2	16.2
Net Income Applicable to Common Stock	509.3	375.8
Less: Earnings Allocated to Participating Securities	4.5	3.6
Earnings Allocated to Common Shares Outstanding	$ 504.8	$ 372.2
Basic Net Income Per Common Share (in dollars per share)	$ 2.72	$ 1.91
Diluted Net Income Per Common Share
Average Number of Common Shares Outstanding (in shares)	185,499,213	195,192,789
Plus: Dilutive Effect of Share-based Compensation (in shares)	1,039,522	932,182
Average Common and Potential Common Shares (in shares)	186,538,735	196,124,971
Earnings Allocated to Common and Potential Common Shares	$ 504.8	$ 372.2
Diluted Net Income Per Common Share (in dollars per share)	$ 2.71	$ 1.90