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Loans and Allowances for Credit Losses, Modifications (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	$ 76.0	$ 147.0
Financing Receivable, Modified, Subsequent Default	$ 14.0	32.0
Number of Days Past Due Following Modification to be Considered a Payment Default	30 days
Commercial [Member] | Extended Maturity
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	$ 48.0	141.0
Financing Receivable, Modified, Subsequent Default		28.0
Commercial real estate [Member]
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	18.0
Healthcare [Member] | Commercial [Member]
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	32.0	90.0
Healthcare [Member] | Commercial [Member] | Extended Maturity
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified, Subsequent Default	5.2
Energy [Member] | Commercial [Member]
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount		43.0
General business [Member] | Commercial [Member]
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	15.0
US Government Agency Insured Loans [Member] | Residential Mortgage [Member] | Loans to individuals [Member]
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	11.0
US Government Agency Insured Loans [Member] | Residential Mortgage [Member] | Loans to individuals [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	11.0	5.9
Financing Receivable, Modified, Subsequent Default	$ 7.1	$ 4.3

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