Loans, Leases, and Allowance for Credit Losses (Summary Aging Analysis, Modified) (Details) $ in Millions	Dec. 31, 2023 USD ($)
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	$ 264
Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	251
30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	13
90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	13
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	69
Commercial | Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	65
Commercial | 30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	4
Commercial | 90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial | Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	4
Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	47
Commercial | Commercial and industrial | Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	44
Commercial | Commercial and industrial | 30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	3
Commercial | Commercial and industrial | 90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial | Commercial and industrial | Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	3
Commercial | Owner-occupied
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	14
Commercial | Owner-occupied | Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	13
Commercial | Owner-occupied | 30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	1
Commercial | Owner-occupied | 90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial | Owner-occupied | Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	1
Commercial | Municipal
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	8
Commercial | Municipal | Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	8
Commercial | Municipal | 30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial | Municipal | 90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial | Municipal | Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	192
Commercial real estate | Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	183
Commercial real estate | 30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	9
Commercial real estate | 90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial real estate | Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	9
Commercial real estate | Construction and land development
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	27
Commercial real estate | Construction and land development | Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	27
Commercial real estate | Construction and land development | 30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial real estate | Construction and land development | 90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial real estate | Construction and land development | Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial real estate | Term
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	165
Commercial real estate | Term | Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	156
Commercial real estate | Term | 30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	9
Commercial real estate | Term | 90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Commercial real estate | Term | Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	9
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	3
Consumer | Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	3
Consumer | 30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Consumer | 90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Consumer | Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Consumer | 1-4 family residential
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	2
Consumer | 1-4 family residential | Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	2
Consumer | 1-4 family residential | 30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Consumer | 1-4 family residential | 90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Consumer | 1-4 family residential | Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Consumer | Bankcard and other revolving plans
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	1
Consumer | Bankcard and other revolving plans | Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	1
Consumer | Bankcard and other revolving plans | 30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Consumer | Bankcard and other revolving plans | 90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	0
Consumer | Bankcard and other revolving plans | Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total	$ 0