Loans, Leases, and Allowance for Credit Losses (Summary of Major Portfolio Segment and Specific Loan Class) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans held for sale	$ 5	$ 8
Total loans and leases	56,331	55,653
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	30,576	30,495
Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	16,500	16,377
Commercial | Leasing
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	385	386
Commercial | Owner-occupied
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	9,317	9,371
Commercial | Municipal
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	4,374	4,361
Commercial | PPP
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	159	197
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	12,898	12,739
Commercial real estate | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	2,313	2,513
Commercial real estate | Term
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	10,585	10,226
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	12,857	12,419
Consumer | Home equity credit line
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	3,276	3,377
Consumer | 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	7,692	7,286
Consumer | Construction and other consumer real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	1,299	1,161
Consumer | Bankcard and other revolving plans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	459	471
Consumer | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans and leases	$ 131	$ 124