Loans, Leases, And Allowance For Credit Losses (Summary Of Past Due Loans (Accruing And Nonaccruing)) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	$ 54,525	$ 48,510
Past Due	220	199
Total loans	54,745	48,709
Accruing loans 90+ days past due	9	10
Nonaccrual loans that are current	352
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	31,386	25,254
Past Due	128	134
Total loans	31,514	25,388
Accruing loans 90+ days past due	6	9
Nonaccrual loans that are current	240
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	11,994	11,539
Past Due	33	16
Total loans	12,027	11,555
Accruing loans 90+ days past due	2	0
Nonaccrual loans that are current	37
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	11,145	11,717
Past Due	59	49
Total loans	11,204	11,766
Accruing loans 90+ days past due	1	1
Nonaccrual loans that are current	75
Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	13,467	14,665
Past Due	76	95
Total loans	13,543	14,760
Accruing loans 90+ days past due	3	8
Nonaccrual loans that are current	158
PPP | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	6,810	0
Past Due	0	0
Total loans	6,810	0
Accruing loans 90+ days past due	0	0
Nonaccrual loans that are current	0
Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	319	334
Past Due	0	0
Total loans	319	334
Accruing loans 90+ days past due	0	1
Nonaccrual loans that are current	1
Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	8,084	7,862
Past Due	52	39
Total loans	8,136	7,901
Accruing loans 90+ days past due	3	0
Nonaccrual loans that are current	81
Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	2,706	2,393
Past Due	0	0
Total loans	2,706	2,393
Accruing loans 90+ days past due	0	0
Nonaccrual loans that are current	0
Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	2,291	2,206
Past Due	7	5
Total loans	2,298	2,211
Accruing loans 90+ days past due	0	0
Nonaccrual loans that are current	0
Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	9,703	9,333
Past Due	26	11
Total loans	9,729	9,344
Accruing loans 90+ days past due	2	0
Nonaccrual loans that are current	37
Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	2,788	2,908
Past Due	9	9
Total loans	2,797	2,917
Accruing loans 90+ days past due	0	0
Nonaccrual loans that are current	16
1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	7,164	7,532
Past Due	45	36
Total loans	7,209	7,568
Accruing loans 90+ days past due	0	0
Nonaccrual loans that are current	59
Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	633	624
Past Due	0	0
Total loans	633	624
Accruing loans 90+ days past due	0	0
Nonaccrual loans that are current	0
Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	427	499
Past Due	4	3
Total loans	431	502
Accruing loans 90+ days past due	1	1
Nonaccrual loans that are current	0
Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Current	133	154
Past Due	1	1
Total loans	134	155
Accruing loans 90+ days past due	0	0
Nonaccrual loans that are current	0
30-89 days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	85	111
30-89 days past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	47	77
30-89 days past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	19	13
30-89 days past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	19	21
30-89 days past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	27	57
30-89 days past due | PPP | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
30-89 days past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
30-89 days past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	20	20
30-89 days past due | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
30-89 days past due | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	7	5
30-89 days past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	12	8
30-89 days past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	6	6
30-89 days past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	9	12
30-89 days past due | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
30-89 days past due | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	3	2
30-89 days past due | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	1	1
90+ days past due
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	135	88
90+ days past due | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	81	57
90+ days past due | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	14	3
90+ days past due | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	40	28
90+ days past due | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	49	38
90+ days past due | PPP | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
90+ days past due | Leasing | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
90+ days past due | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	32	19
90+ days past due | Municipal | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
90+ days past due | Construction and land development | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
90+ days past due | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	14	3
90+ days past due | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	3	3
90+ days past due | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	36	24
90+ days past due | Construction and other consumer real estate | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
90+ days past due | Bankcard and other revolving plans | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	1	1
90+ days past due | Other | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Past Due	0	0
Nonaccrual loans that are current
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	199	129
Nonaccrual loans that are current | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	152	98
Nonaccrual loans that are current | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	18	11
Nonaccrual loans that are current | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	29	20
Nonaccrual loans that are current | Commercial and industrial | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	106	54
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	1	0
Nonaccrual loans that are current | Owner-occupied | Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	45	44
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	1
Nonaccrual loans that are current | Term | Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	18	10
Nonaccrual loans that are current | Home equity credit line | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	9	7
Nonaccrual loans that are current | 1-4 family residential | Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans that are current	19	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	$ 0	$ 0