Loans, Leases, and Allowance for Credit Losses (Summary of Past Due Loans (Accruing and Nonaccruing)) (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 52,370	$ 50,851
90+ days past due	6	8
Nonaccrual loans that are current	195	271
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	29,183	28,440
90+ days past due	2	7
Nonaccrual loans that are current	127	184
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12,136	12,198
90+ days past due	3	0
Nonaccrual loans that are current	20	20
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	11,051	10,213
90+ days past due	1	1
Nonaccrual loans that are current	48	67
Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	14,989	13,867
90+ days past due	0	2
Nonaccrual loans that are current	86	124
PPP | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	534	1,855
90+ days past due	0	5
Nonaccrual loans that are current	1	3
Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	339	327
90+ days past due	0	0
Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,208	8,733
90+ days past due	2	0
Nonaccrual loans that are current	40	57
Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,113	3,658
90+ days past due	0	0
Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,659	2,757
90+ days past due	0	0
Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,477	9,441
90+ days past due	3	0
Nonaccrual loans that are current	20	20
Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,266	3,016
90+ days past due	0	0
Nonaccrual loans that are current	10	14
1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	6,423	6,050
90+ days past due	0	0
Nonaccrual loans that are current	38	52
Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	787	638
90+ days past due	0	0
Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	448	396
90+ days past due	1	1
Nonaccrual loans that are current	0	1
Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	127	113
90+ days past due	0	0
Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	52,183	50,684
Current | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	29,106	28,332
Current | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12,059	12,183
Current | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	11,018	10,169
Current | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	14,937	13,822
Current | PPP | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	526	1,813
Current | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	339	327
Current | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,191	8,712
Current | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,113	3,658
Current | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,636	2,757
Current | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,423	9,426
Current | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,260	3,008
Current | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	6,399	6,018
Current | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	787	638
Current | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	446	393
Current | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	126	112
Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	187	167
Total past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	77	108
Total past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	77	15
Total past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	33	44
Total past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	52	45
Total past due | PPP | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	8	42
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	17	21
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	23	0
Total past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	54	15
Total past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	6	8
Total past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	24	32
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	2	3
Total past due | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	1
30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	128	82
30-89 days past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	48	59
30-89 days past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	68	10
30-89 days past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	12	13
30-89 days past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	31	17
30-89 days past due | PPP | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	7	35
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	10	7
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	23	0
30-89 days past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	45	10
30-89 days past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4	4
30-89 days past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	6	6
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	1	2
30-89 days past due | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	1
90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	59	85
90+ days past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	29	49
90+ days past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9	5
90+ days past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	21	31
90+ days past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	21	28
90+ days past due | PPP | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1	7
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	7	14
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	9	5
90+ days past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2	4
90+ days past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	18	26
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	137	182
Nonaccrual loans that are current | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	97	133
Nonaccrual loans that are current | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	15	15
Nonaccrual loans that are current | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	25	34
Nonaccrual loans that are current | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	64	91
Nonaccrual loans that are current | PPP | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	0	0
Nonaccrual loans that are current | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	0	0
Nonaccrual loans that are current | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	33	42
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	15	15
Nonaccrual loans that are current | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	6	10
Nonaccrual loans that are current | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	19	24
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