CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Available-for-sale securities, amortized cost	$ 37,065.7	$ 34,102.4
Held to maturity, fair value	23,138.0	22,381.2
Unearned income	$ 5.1	$ 5.3
Preferred stock, authorized (in shares)	10,000,000	10,000,000
Common stock, par value (in usd per share)	$ 1.6667	$ 1.6667
Common stock, authorized (in shares)	560,000,000	560,000,000
Common stock, outstanding (in shares)	185,047,258	186,337,588
Treasury stock (in shares)	60,124,266	58,833,936
Series D Preferred Stock
Preferred stock, authorized (in shares)	5,000	5,000
Preferred stock, outstanding (in shares)	5,000	5,000
Series E Preferred Stock
Preferred stock, authorized (in shares)	16,000	16,000
Preferred stock, outstanding (in shares)	16,000	16,000