Fair Value Measurements - Fair Value of Financial Instruments Not Measured at Fair Value on a Recurring Basis (Details) - USD ($)	Dec. 31, 2025	Dec. 31, 2024
ASSETS
Cash and Due from Banks	$ 5,873,100,000	$ 4,677,200,000
Federal Reserve and Other Central Bank Deposits	53,524,900,000	38,775,400,000
Interest-Bearing Deposits with Banks	1,729,400,000	1,944,700,000
Federal Funds Sold and Securities Purchased under Agreements to Resell	2,654,100,000	451,000,000.0
FAIR VALUE	22,381,200,000	20,654,500,000
Loans
Held for Sale	6,800,000	6,800,000
LIABILITIES
Deposits	142,797,700,000	122,482,700,000
Federal Funds Purchased	2,141,100,000	2,159,500,000
Balance at December 31	292,200,000	462,000,000.0
Other Borrowings	7,158,300,000	6,521,000,000
Senior Notes	3,351,500,000	2,769,700,000
Unfunded Commitments	19,600,000	0
CARRYING  VALUE
ASSETS
Cash and Due from Banks	5,873,100,000	4,677,200,000
Federal Reserve and Other Central Bank Deposits	53,524,900,000	38,775,400,000
Interest-Bearing Deposits with Banks	1,729,400,000	1,944,700,000
Federal Funds Sold and Securities Purchased under Agreements to Resell	2,654,100,000	451,000,000.0
FAIR VALUE	23,429,600,000	22,296,700,000
Loans
Held for Investment	41,777,100,000	43,222,500,000
Held for Sale	6,800,000
Other Assets	1,668,600,000	1,506,400,000
LIABILITIES
Deposits	142,797,700,000	122,482,700,000
Federal Funds Purchased	2,141,100,000	2,159,500,000
Balance at December 31	292,200,000	462,000,000.0
Other Borrowings	7,158,300,000	6,521,000,000
Senior Notes	3,351,500,000	2,769,700,000
Long-Term Debt	3,484,400,000	4,081,300,000
Unfunded Commitments	373,000,000.0	227,100,000
Other Liabilities	37,900,000	50,600,000
FAIR VALUE
ASSETS
Cash and Due from Banks	5,873,100,000	4,677,200,000
Federal Reserve and Other Central Bank Deposits	53,524,900,000	38,775,400,000
Interest-Bearing Deposits with Banks	1,729,400,000	1,944,700,000
Federal Funds Sold and Securities Purchased under Agreements to Resell	2,654,100,000	451,000,000.0
FAIR VALUE	22,381,200,000	20,654,500,000
Loans
Held for Investment	41,661,200,000	42,803,200,000
Held for Sale	6,800,000
Other Assets	1,664,800,000	1,499,200,000
LIABILITIES
Deposits	142,348,600,000	122,536,500,000
Federal Funds Purchased	2,141,100,000	2,159,500,000
Balance at December 31	292,200,000	462,000,000.0
Other Borrowings	7,185,500,000	6,545,300,000
Senior Notes	3,405,500,000	2,800,300,000
Long-Term Debt	3,596,800,000	4,164,400,000
Unfunded Commitments	373,000,000.0	227,100,000
Other Liabilities	37,900,000	50,600,000
FAIR VALUE | LEVEL 1
ASSETS
Cash and Due from Banks	5,873,100,000	4,677,200,000
Federal Reserve and Other Central Bank Deposits	0	0
Interest-Bearing Deposits with Banks	0	0
Federal Funds Sold and Securities Purchased under Agreements to Resell	0	0
FAIR VALUE	0	0
Loans
Held for Investment	0	0
Held for Sale	0
Other Assets	86,300,000	83,300,000
LIABILITIES
Deposits	0	0
Federal Funds Purchased	0	0
Balance at December 31	0	0
Other Borrowings	0	0
Senior Notes	0	0
Long-Term Debt	0	0
Unfunded Commitments	0	0
Other Liabilities	0	0
FAIR VALUE | LEVEL 2
ASSETS
Cash and Due from Banks	0	0
Federal Reserve and Other Central Bank Deposits	53,524,900,000	38,775,400,000
Interest-Bearing Deposits with Banks	1,729,400,000	1,944,700,000
Federal Funds Sold and Securities Purchased under Agreements to Resell	2,654,100,000	451,000,000.0
FAIR VALUE	22,381,200,000	20,654,500,000
Loans
Held for Investment	0	0
Held for Sale	6,800,000
Other Assets	1,578,500,000	1,415,900,000
LIABILITIES
Deposits	142,348,600,000	122,536,500,000
Federal Funds Purchased	2,141,100,000	2,159,500,000
Balance at December 31	292,200,000	462,000,000.0
Other Borrowings	7,185,500,000	6,545,300,000
Senior Notes	3,405,500,000	2,800,300,000
Long-Term Debt	3,596,800,000	4,164,400,000
Unfunded Commitments	373,000,000.0	227,100,000
Other Liabilities	0	0
FAIR VALUE | LEVEL 3
ASSETS
Cash and Due from Banks	0	0
Federal Reserve and Other Central Bank Deposits	0	0
Interest-Bearing Deposits with Banks	0	0
Federal Funds Sold and Securities Purchased under Agreements to Resell	0	0
FAIR VALUE	0	0
Loans
Held for Investment	41,661,200,000	42,803,200,000
Held for Sale
Other Assets	0	0
LIABILITIES
Deposits	0	0
Federal Funds Purchased	0	0
Balance at December 31	0	0
Other Borrowings	0	0
Senior Notes	0	0
Long-Term Debt	0	0
Unfunded Commitments	0	0
Other Liabilities	$ 37,900,000	$ 50,600,000