Loans, Leases, and Allowance for Credit Losses (Summary of Past Due Loans (Accruing and Nonaccruing)) (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 58,415	$ 57,779
90+ days past due	6	3
Nonaccrual loans that are current	261	222
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	30,511	30,588
90+ days past due	5	2
Nonaccrual loans that are current	147	104
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	13,549	13,371
90+ days past due	0	0
Nonaccrual loans that are current	37	61
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	14,355	13,820
90+ days past due	1	1
Nonaccrual loans that are current	77	57
Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	16,622	16,684
90+ days past due	4	1
Nonaccrual loans that are current	111	82
Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	390	383
90+ days past due	0	0
Nonaccrual loans that are current	2	2
Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,236	9,219
90+ days past due	1	1
Nonaccrual loans that are current	28	20
Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,263	4,302
90+ days past due	0	0
Nonaccrual loans that are current	6
Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,725	2,669
90+ days past due	0	0
Nonaccrual loans that are current	2	22
Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10,824	10,702
90+ days past due	0	0
Nonaccrual loans that are current	35	39
Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,468	3,356
90+ days past due	0	0
Nonaccrual loans that are current	29	17
1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,153	8,415
90+ days past due	0	0
Nonaccrual loans that are current	46	40
Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,139	1,442
90+ days past due	0	0
Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	466	474
90+ days past due	1	1
Nonaccrual loans that are current	1
Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	129	133
90+ days past due	0	0
Nonaccrual loans that are current	1
Current
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	58,202	57,576
Current | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	30,436	30,519
Current | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	13,484	13,306
Current | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	14,282	13,751
Current | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	16,577	16,631
Current | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	388	381
Current | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,223	9,206
Current | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,248	4,301
Current | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,723	2,645
Current | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10,761	10,661
Current | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,440	3,334
Current | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,112	8,375
Current | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,139	1,442
Current | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	463	468
Current | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	128	132
Total past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	213	203
Total past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	75	69
Total past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	65	65
Total past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	73	69
Total past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	45	53
Total past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2	2
Total past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	13	13
Total past due | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	15	1
Total past due | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2	24
Total past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	63	41
Total past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	28	22
Total past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	41	40
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	3	6
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	131	108
30-89 days past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	55	52
30-89 days past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	38	16
30-89 days past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	38	40
30-89 days past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	30	38
30-89 days past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	2
30-89 days past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10	11
30-89 days past due | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	15	1
30-89 days past due | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0	2
30-89 days past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	38	14
30-89 days past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	18	17
30-89 days past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	17	17
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	2	5
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	82	95
90+ days past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	20	17
90+ days past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	27	49
90+ days past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	35	29
90+ days past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	15	15
90+ days past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2	0
90+ days past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3	2
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	2	22
90+ days past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	25	27
90+ days past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10	5
90+ days past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	24	23
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	168	108
Nonaccrual loans that are current | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	126	83
Nonaccrual loans that are current | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	10	3
Nonaccrual loans that are current | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	32	22
Nonaccrual loans that are current | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	98	65
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	22	18
Nonaccrual loans that are current | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	6	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	10	3
Nonaccrual loans that are current | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	13	9
Nonaccrual loans that are current | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	17	13
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	1	0
Nonaccrual loans that are current | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	$ 1	$ 0