Loans, Leases, and Allowance for Credit Losses (Summary of Outstanding Loan Balances (Accruing and Nonaccruing) Categorized by Credit Quality Indicators - Current Year) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022
Total loans
2023	$ 8,155	$ 13,059
2022	12,553	10,344
2021	8,774	6,360
2020	4,982	4,239
2019	3,222	2,347
Prior	6,610	5,667
Revolving loans amortized cost basis	12,896	13,064
Revolving loans converted to term loans amortized cost basis	587	573
Total loans	57,779	55,653
Gross charge-offs
2023	1
2022	12
2021	6
2020	0
2019	1
Prior	4
Revolving loans amortized cost basis	36
Revolving loans converted to term loans amortized cost basis	2
Total	62	82
Commercial
Total loans
2023	4,492	6,987
2022	5,770	5,522
2021	4,436	3,072
2020	2,336	2,430
2019	1,729	1,228
Prior	3,201	2,568
Revolving loans amortized cost basis	8,410	8,426
Revolving loans converted to term loans amortized cost basis	214	262
Total loans	30,588	30,495
Gross charge-offs
2023	1
2022	10
2021	6
2020	0
2019	0
Prior	2
Revolving loans amortized cost basis	24
Revolving loans converted to term loans amortized cost basis	2
Total	45	72
Commercial real estate
Total loans
2023	2,571	3,508
2022	3,477	2,802
2021	2,294	2,186
2020	1,634	1,140
2019	884	726
Prior	1,482	1,276
Revolving loans amortized cost basis	757	893
Revolving loans converted to term loans amortized cost basis	272	208
Total loans	13,371	12,739
Gross charge-offs
2023	0
2022	2
2021	0
2020	0
2019	1
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total	3	0
Consumer
Total loans
2023	1,092	2,564
2022	3,306	2,020
2021	2,044	1,102
2020	1,012	669
2019	609	393
Prior	1,927	1,823
Revolving loans amortized cost basis	3,729	3,745
Revolving loans converted to term loans amortized cost basis	101	103
Total loans	13,820	12,419
Gross charge-offs
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	2
Revolving loans amortized cost basis	12
Revolving loans converted to term loans amortized cost basis	0
Total	14	10
Commercial and industrial \| Commercial
Total loans
2023	2,678	3,390
2022	2,572	1,891
2021	1,246	1,011
2020	645	1,017
2019	544	325
Prior	644	335
Revolving loans amortized cost basis	8,196	8,220
Revolving loans converted to term loans amortized cost basis	159	188
Total loans	16,684	16,377
Gross charge-offs
2023	1
2022	10
2021	6
2020	0
2019	0
Prior	2
Revolving loans amortized cost basis	24
Revolving loans converted to term loans amortized cost basis	2
Total	45
Leasing \| Commercial
Total loans
2023	106	160
2022	136	71
2021	48	47
2020	30	66
2019	45	18
Prior	18	24
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	383	386
Gross charge-offs
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total	0
Owner-occupied \| Commercial
Total loans
2023	1,092	2,175
2022	1,982	2,334
2021	2,067	1,198
2020	1,035	906
2019	757	717
Prior	2,020	1,769
Revolving loans amortized cost basis	214	198
Revolving loans converted to term loans amortized cost basis	52	74
Total loans	9,219	9,371
Gross charge-offs
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total	0
Municipal \| Commercial
Total loans
2023	616	1,262
2022	1,080	1,226
2021	1,075	816
2020	626	441
2019	383	168
Prior	519	440
Revolving loans amortized cost basis	0	8
Revolving loans converted to term loans amortized cost basis	3	0
Total loans	4,302	4,361
Gross charge-offs
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total	0
Construction and land development \| Commercial real estate
Total loans
2023	576	566
2022	940	672
2021	384	455
2020	91	103
2019	28	2
Prior	4	2
Revolving loans amortized cost basis	519	617
Revolving loans converted to term loans amortized cost basis	127	96
Total loans	2,669	2,513
Gross charge-offs
2023	0
2022	0
2021	0
2020	0
2019	1
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total	1
Term \| Commercial real estate
Total loans
2023	1,995	2,942
2022	2,537	2,130
2021	1,910	1,731
2020	1,543	1,037
2019	856	724
Prior	1,478	1,274
Revolving loans amortized cost basis	238	276
Revolving loans converted to term loans amortized cost basis	145	112
Total loans	10,702	10,226
Gross charge-offs
2023	0
2022	2
2021	0
2020	0
2019	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total	2
Home equity credit line \| Consumer
Total loans
2023	0	0
2022	0	0
2021	0	0
2020	0	0
2019	0	0
Prior	0	0
Revolving loans amortized cost basis	3,256	3,276
Revolving loans converted to term loans amortized cost basis	100	101
Total loans	3,356	3,377
Gross charge-offs
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Revolving loans amortized cost basis	3
Revolving loans converted to term loans amortized cost basis	0
Total	3
1-4 family residential \| Consumer
Total loans
2023	814	1,913
2022	2,267	1,505
2021	1,826	1,026
2020	991	642
2019	598	384
Prior	1,919	1,816
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	8,415	7,286
Gross charge-offs
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	2
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total	2
Construction and other consumer real estate \| Consumer
Total loans
2023	212	583
2022	1,002	485
2021	200	64
2020	15	19
2019	7	5
Prior	6	5
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	1,442	1,161
Gross charge-offs
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total	0
Bankcard and other revolving plans \| Consumer
Total loans
2023	0	0
2022	0	0
2021	0	0
2020	0	0
2019	0	0
Prior	0	0
Revolving loans amortized cost basis	473	469
Revolving loans converted to term loans amortized cost basis	1	2
Total loans	474	471
Gross charge-offs
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Revolving loans amortized cost basis	9
Revolving loans converted to term loans amortized cost basis	0
Total	9
Other \| Consumer
Total loans
2023	66	68
2022	37	30
2021	18	12
2020	6	8
2019	4	4
Prior	2	2
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	133	124
Gross charge-offs
2023	0
2022	0
2021	0
2020	0
2019	0
Prior	0
Revolving loans amortized cost basis	0
Revolving loans converted to term loans amortized cost basis	0
Total	0
Pass \| Commercial and industrial \| Commercial
Total loans
2023	2,654	3,363
2022	2,420	1,874
2021	1,204	979
2020	639	876
2019	494	293
Prior	598	264
Revolving loans amortized cost basis	7,973	8,054
Revolving loans converted to term loans amortized cost basis	151	182
Total loans	16,133	15,885
Pass \| Leasing \| Commercial
Total loans
2023	104	160
2022	125	71
2021	47	47
2020	29	66
2019	45	18
Prior	18	19
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	368	381
Pass \| Owner-occupied \| Commercial
Total loans
2023	1,080	2,157
2022	1,945	2,285
2021	2,020	1,143
2020	1,002	874
2019	721	654
Prior	1,907	1,679
Revolving loans amortized cost basis	212	187
Revolving loans converted to term loans amortized cost basis	52	74
Total loans	8,939	9,053
Pass \| Municipal \| Commercial
Total loans
2023	601	1,230
2022	1,080	1,220
2021	1,069	816
2020	623	441
2019	382	168
Prior	512	437
Revolving loans amortized cost basis	0	8
Revolving loans converted to term loans amortized cost basis	3	0
Total loans	4,270	4,320
Pass \| Construction and land development \| Commercial real estate
Total loans
2023	553	548
2022	938	671
2021	355	455
2020	56	81
2019	7	2
Prior	4	2
Revolving loans amortized cost basis	518	617
Revolving loans converted to term loans amortized cost basis	127	96
Total loans	2,558	2,472
Pass \| Term \| Commercial real estate
Total loans
2023	1,861	2,861
2022	2,385	2,107
2021	1,833	1,686
2020	1,449	1,012
2019	804	666
Prior	1,438	1,229
Revolving loans amortized cost basis	238	276
Revolving loans converted to term loans amortized cost basis	110	112
Total loans	10,118	9,949
Pass \| Home equity credit line \| Consumer
Total loans
2023	0	0
2022	0	0
2021	0	0
2020	0	0
2019	0	0
Prior	0	0
Revolving loans amortized cost basis	3,237	3,265
Revolving loans converted to term loans amortized cost basis	97	98
Total loans	3,334	3,363
Pass \| 1-4 family residential \| Consumer
Total loans
2023	814	1,913
2022	2,264	1,503
2021	1,823	1,024
2020	988	638
2019	594	381
Prior	1,891	1,788
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	8,374	7,247
Pass \| Construction and other consumer real estate \| Consumer
Total loans
2023	212	583
2022	1,002	485
2021	200	64
2020	15	19
2019	7	5
Prior	6	5
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	1,442	1,161
Pass \| Bankcard and other revolving plans \| Consumer
Total loans
2023	0	0
2022	0	0
2021	0	0
2020	0	0
2019	0	0
Prior	0	0
Revolving loans amortized cost basis	471	468
Revolving loans converted to term loans amortized cost basis	1	2
Total loans	472	470
Pass \| Other \| Consumer
Total loans
2023	66	68
2022	37	30
2021	18	12
2020	6	8
2019	4	4
Prior	2	2
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	133	124
Special Mention \| Commercial and industrial \| Commercial
Total loans
2023	8	1
2022	98	2
2021	34	10
2020	2	52
2019	20	1
Prior	37	2
Revolving loans amortized cost basis	103	50
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	302	118
Special Mention \| Leasing \| Commercial
Total loans
2023	2	0
2022	9	0
2021	1	0
2020	1	0
2019	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	13	0
Special Mention \| Owner-occupied \| Commercial
Total loans
2023	2	1
2022	5	15
2021	17	5
2020	5	8
2019	17	3
Prior	15	16
Revolving loans amortized cost basis	0	1
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	61	49
Special Mention \| Municipal \| Commercial
Total loans
2023	7	32
2022	0	6
2021	0	0
2020	0	0
2019	0	0
Prior	6	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	13	38
Special Mention \| Construction and land development \| Commercial real estate
Total loans
2023	0	1
2022	0	1
2021	29	0
2020	30	0
2019	0	0
Prior	0	0
Revolving loans amortized cost basis	0	0
Revolving loans converted to term loans amortized cost basis	0	0
Total loans	59	2
Special Mention \| Term \| Commercial real estate
Total loans
2023	55	39
2022	108	21
2021	65	11
2020	78	0
2019	44	4
Prior	6	1
Revolving loans amortized cost basis	0	0

Loans, Leases, and Allowance for Credit Losses (Summary of Outstanding Loan Balances (Accruing and Nonaccruing) Categorized by Credit Quality Indicators - Current Year) (Details) - USD ($)
$ in Millions