Loans and Allowances for Credit Losses, Modifications (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	$ 114.0	$ 58.0
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	$ 110.0
Healthcare [Member] | Commercial [Member]
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	90.0	37.0
Healthcare [Member] | Commercial [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount		26.0
General business [Member] | Commercial [Member]
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount		10.0
Healthcare, Services and General business member | Extended Maturity
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount		20.0
Residential Mortgage [Member] | Loans to individuals [Member]
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified, Subsequent Default		4.4
Energy [Member] | Commercial [Member]
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	14.0
US Government Agency Insured Loans [Member] | Loans to individuals [Member] | Extended Maturity and Interest Rate Reduction
Financing Receivable, Loan Modifications [Line Items]
Financing Receivable, Modified in Period, Amount	4.1	11.0
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
Financing Receivable, Modified, Subsequent Default	$ 1.1	$ 4.3