Loans, Leases, and Allowance for Credit Losses (Summary of Past Due Loans (Accruing and Nonaccruing)) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 56,331	$ 55,653
90+ days past due	2	6
Nonaccrual loans that are current	171	149
Loans and leases, net of unearned income and fees	56,331	55,653
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	30,576	30,495
90+ days past due	1	5
Nonaccrual loans that are current	110	87
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12,898	12,739
90+ days past due	0	0
Nonaccrual loans that are current	16	14
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12,857	12,419
90+ days past due	1	1
Nonaccrual loans that are current	45	48
Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	16,500	16,377
90+ days past due	1	4
Nonaccrual loans that are current	77	63
Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	385	386
90+ days past due	0	0
Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,317	9,371
90+ days past due	0	1
Nonaccrual loans that are current	33	24
Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,374	4,361
90+ days past due	0	0
Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,313	2,513
90+ days past due	0	0
Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10,585	10,226
90+ days past due	0	0
Nonaccrual loans that are current	16	14
Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,276	3,377
90+ days past due	0	0
Nonaccrual loans that are current	11	11
1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	7,692	7,286
90+ days past due	0	0
Nonaccrual loans that are current	34	37
Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,299	1,161
90+ days past due	0	0
Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	459	471
90+ days past due	1	1
Nonaccrual loans that are current		0
Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	131	124
90+ days past due	0	0
Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	56,204	55,491
Current | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	30,500	30,422
Current | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12,890	12,690
Current | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12,814	12,379
Current | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	16,436	16,331
Current | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	385	386
Current | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,305	9,344
Current | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,374	4,361
Current | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,308	2,511
Current | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10,582	10,179
Current | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,265	3,369
Current | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	7,665	7,258
Current | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,299	1,161
Current | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	455	467
Current | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	130	124
Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	127	162
Total past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	76	73
Total past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	8	49
Total past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	43	40
Total past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	64	46
Total past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
Total past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12	27
Total past due | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
Total past due | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	5	2
Total past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3	47
Total past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	11	8
Total past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	27	28
Total past due | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
Total past due | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4	4
Total past due | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	0
30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	94	100
30-89 days past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	62	44
30-89 days past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	6	39
30-89 days past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	26	17
30-89 days past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	53	24
30-89 days past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
30-89 days past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9	20
30-89 days past due | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
30-89 days past due | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	5	2
30-89 days past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	37
30-89 days past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	8	5
30-89 days past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	14	9
30-89 days past due | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
30-89 days past due | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3	3
30-89 days past due | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	0
90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	33	62
90+ days past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	14	29
90+ days past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2	10
90+ days past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	17	23
90+ days past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	11	22
90+ days past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
90+ days past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3	7
90+ days past due | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
90+ days past due | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
90+ days past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2	10
90+ days past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3	3
90+ days past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	13	19
90+ days past due | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
90+ days past due | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	1
90+ days past due | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	0
Nonaccrual loans that are current
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	126	86
Nonaccrual loans that are current | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	93	60
Nonaccrual loans that are current | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	14	4
Nonaccrual loans that are current | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	19	22
Nonaccrual loans that are current | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	64	45
Nonaccrual loans that are current | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	1	0
Nonaccrual loans that are current | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	28	15
Nonaccrual loans that are current | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	0	0
Nonaccrual loans that are current | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	0	0
Nonaccrual loans that are current | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	14	4
Nonaccrual loans that are current | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	5	6
Nonaccrual loans that are current | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	14	16
Nonaccrual loans that are current | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	0	0
Nonaccrual loans that are current | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	0	0
Nonaccrual loans that are current | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	$ 0	$ 0