Loans, Leases, And Allowance For Credit Losses (Summary Of Outstanding Loan Balances (Accruing And Nonaccruing) Categorized By Credit Quality Indicators) (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	$ 14,069
2019	10,375
2018	7,853
2017	5,097
2016	3,458
Prior	6,183
Revolving loans amortized cost basis	7,425
Revolving loans converted to term loans amortized cost basis	285
Total loans	54,745	$ 48,709
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	10,510
2019	5,945
2018	4,301
2017	2,768
2016	1,256
Prior	2,767
Revolving loans amortized cost basis	3,845
Revolving loans converted to term loans amortized cost basis	122
Total loans	31,514	25,388
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	2,505
2019	2,962
2018	2,464
2017	1,078
2016	901
Prior	1,602
Revolving loans amortized cost basis	490
Revolving loans converted to term loans amortized cost basis	25
Total loans	12,027	11,555
Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	1,054
2019	1,468
2018	1,088
2017	1,251
2016	1,301
Prior	1,814
Revolving loans amortized cost basis	3,090
Revolving loans converted to term loans amortized cost basis	138
Total loans	11,204	11,766
Commercial and industrial \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	1,803
2019	3,521
2018	2,493
2017	1,206
2016	399
Prior	362
Revolving loans amortized cost basis	3,658
Revolving loans converted to term loans amortized cost basis	101
Total loans	13,543	14,760
PPP \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	6,810
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	6,810	0
Leasing \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	66
2019	130
2018	51
2017	39
2016	19
Prior	14
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	319	334
Owner-occupied \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	1,168
2019	1,426
2018	1,362
2017	1,081
2016	762
Prior	2,132
Revolving loans amortized cost basis	184
Revolving loans converted to term loans amortized cost basis	21
Total loans	8,136	7,901
Municipal \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	663
2019	868
2018	395
2017	442
2016	76
Prior	259
Revolving loans amortized cost basis	3
Revolving loans converted to term loans amortized cost basis	0
Total loans	2,706	2,393
Construction and land development \| Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	495
2019	907
2018	398
2017	73
2016	1
Prior	7
Revolving loans amortized cost basis	414
Revolving loans converted to term loans amortized cost basis	3
Total loans	2,298	2,211
Term \| Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	2,010
2019	2,055
2018	2,066
2017	1,005
2016	900
Prior	1,595
Revolving loans amortized cost basis	76
Revolving loans converted to term loans amortized cost basis	22
Total loans	9,729	9,344
Home equity credit line \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	2,661
Revolving loans converted to term loans amortized cost basis	136
Total loans	2,797	2,917
1-4 family residential \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	889
2019	1,087
2018	920
2017	1,219
2016	1,295
Prior	1,799
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	7,209	7,568
Construction and other consumer real estate \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	119
2019	339
2018	141
2017	20
2016	1
Prior	13
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	633	624
Bankcard and other revolving plans \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	429
Revolving loans converted to term loans amortized cost basis	2
Total loans	431	502
Other \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	46
2019	42
2018	27
2017	12
2016	5
Prior	2
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	134	$ 155
Pass \| Commercial and industrial \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	1,613
2019	3,192
2018	2,082
2017	994
2016	372
Prior	284
Revolving loans amortized cost basis	3,405
Revolving loans converted to term loans amortized cost basis	85
Total loans	12,027
Pass \| PPP \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	6,810
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	6,810
Pass \| Leasing \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	64
2019	117
2018	47
2017	36
2016	17
Prior	8
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	289
Pass \| Owner-occupied \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	1,083
2019	1,312
2018	1,234
2017	956
2016	664
Prior	1,956
Revolving loans amortized cost basis	154
Revolving loans converted to term loans amortized cost basis	17
Total loans	7,376
Pass \| Municipal \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	663
2019	868
2018	374
2017	442
2016	76
Prior	242
Revolving loans amortized cost basis	3
Revolving loans converted to term loans amortized cost basis	0
Total loans	2,668
Pass \| Construction and land development \| Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	467
2019	871
2018	388
2017	52
2016	1
Prior	7
Revolving loans amortized cost basis	407
Revolving loans converted to term loans amortized cost basis	3
Total loans	2,196
Pass \| Term \| Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	1,862
2019	1,886
2018	1,840
2017	917
2016	866
Prior	1,438
Revolving loans amortized cost basis	75
Revolving loans converted to term loans amortized cost basis	22
Total loans	8,906
Pass \| Home equity credit line \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	2,640
Revolving loans converted to term loans amortized cost basis	130
Total loans	2,770
Pass \| 1-4 family residential \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	889
2019	1,085
2018	915
2017	1,209
2016	1,288
Prior	1,758
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	7,144
Pass \| Construction and other consumer real estate \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	119
2019	339
2018	141
2017	20
2016	1
Prior	13
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	633
Pass \| Bankcard and other revolving plans \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	425
Revolving loans converted to term loans amortized cost basis	2
Total loans	427
Pass \| Other \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	46
2019	42
2018	27
2017	12
2016	5
Prior	2
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	134
Special Mention \| Commercial and industrial \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	50
2019	212
2018	181
2017	99
2016	7
Prior	44
Revolving loans amortized cost basis	98
Revolving loans converted to term loans amortized cost basis	1
Total loans	692
Special Mention \| PPP \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	0
Special Mention \| Leasing \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	11
2018	3
2017	2
2016	1
Prior	6
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	23
Special Mention \| Owner-occupied \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	55
2019	50
2018	50
2017	75
2016	56
Prior	40
Revolving loans amortized cost basis	12
Revolving loans converted to term loans amortized cost basis	2
Total loans	340
Special Mention \| Municipal \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	10
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	10
Special Mention \| Construction and land development \| Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	28
2019	32
2018	10
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	7
Revolving loans converted to term loans amortized cost basis	0
Total loans	77
Special Mention \| Term \| Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	93
2019	139
2018	163
2017	54
2016	17
Prior	100
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	566
Accruing Substandard \| Commercial and industrial \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	98
2019	110
2018	222
2017	76
2016	18
Prior	17
Revolving loans amortized cost basis	120
Revolving loans converted to term loans amortized cost basis	5
Total loans	666
Accruing Substandard \| PPP \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	0
Accruing Substandard \| Leasing \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	2
2019	2
2018	1
2017	1
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	6
Accruing Substandard \| Owner-occupied \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	25
2019	50
2018	62
2017	38
2016	35
Prior	111
Revolving loans amortized cost basis	17
Revolving loans converted to term loans amortized cost basis	1
Total loans	339
Accruing Substandard \| Municipal \| Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	21
2017	0
2016	0
Prior	7
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	28
Accruing Substandard \| Construction and land development \| Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	4
2018	0
2017	21
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	25
Accruing Substandard \| Term \| Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	55
2019	25
2018	63
2017	31
2016	16
Prior	30
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	220
Accruing Substandard \| Home equity credit line \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	10
Revolving loans converted to term loans amortized cost basis	1
Total loans	11
Accruing Substandard \| 1-4 family residential \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	1
2017	0
2016	1
Prior	4
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	6
Accruing Substandard \| Construction and other consumer real estate \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total loans	0
Accruing Substandard \| Bankcard and other revolving plans \| Consumer
Financing Receivable, Allowance for Credit Losses [Line Items]
2020	0
2019	0
2018	0
2017	0

Loans, Leases, And Allowance For Credit Losses (Summary Of Outstanding Loan Balances (Accruing And Nonaccruing) Categorized By Credit Quality Indicators) (Details) - USD ($)
$ in Millions