Loans And Allowance For Credit Losses - Schedule of Company's Internal Ratings of its Loans Held-for-Investment, Including The Year of Origination, by Portfolio Segments (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Financing Receivable Recorded Investment [Line Items]
2024	$ 3,112	$ 2,531
2023	1,205	2,036
2022	1,571	1,062
2021	836	518
2020	355	240
Prior	637	613
Revolving Loans Amort Cost Basis	198	149
Total Past Due	7,914	7,149
Charge off [Member]
Financing Receivable Recorded Investment [Line Items]
2023	3	1
2022	2	1
Total Past Due	5	2
Agricultural [Member]
Financing Receivable Recorded Investment [Line Items]
2024	79	64
2023	8	15
2022	5	4
2021	2	1
2020	1	1
Prior		0
Total Past Due	95	85
Pass [Member]
Financing Receivable Recorded Investment [Line Items]
2024	3,057	2,488
2023	1,173	2,007
2022	1,506	1,041
2021	802	499
2020	338	214
Prior	608	578
Revolving Loans Amort Cost Basis	196	145
Total Past Due	7,680	6,972
Pass [Member] | Agricultural [Member]
Financing Receivable Recorded Investment [Line Items]
2024	76	63
2023	8	15
2022	4	4
2021	2	1
2020	1	1
Prior		0
Total Past Due	91	84
Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
2024	15	11
2023	3	11
2022	8	7
2021	11	2
2020	1	2
Prior	4	6
Revolving Loans Amort Cost Basis	0	1
Total Past Due	42	40
Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
2024	40	32
2023	29	18
2022	57	14
2021	23	17
2020	16	24
Prior	25	29
Revolving Loans Amort Cost Basis	2	3
Total Past Due	192	137
Substandard [Member] | Agricultural [Member]
Financing Receivable Recorded Investment [Line Items]
2024	3	1
2022	1
Total Past Due	4	1
C&I [Member]
Financing Receivable Recorded Investment [Line Items]
2024	696	733
2023	229	279
2022	151	75
2021	46	37
2020	24	16
Prior	31	25
Revolving Loans Amort Cost Basis	0
Total Past Due	1,177	1,165
C&I [Member] | Charge off [Member]
Financing Receivable Recorded Investment [Line Items]
2023	1
2022		1
Total Past Due	1	1
C&I [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
2024	677	720
2023	226	276
2022	146	73
2021	45	36
2020	23	14
Prior	30	23
Revolving Loans Amort Cost Basis	0
Total Past Due	1,147	1,142
C&I [Member] | Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
2024	7	1
2023		1
2022	1
2021	0
2020	1	1
Prior	0
Revolving Loans Amort Cost Basis	0
Total Past Due	9	3
C&I [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
2024	12	12
2023	3	2
2022	4	2
2021	1	1
2020	0	1
Prior	1	2
Revolving Loans Amort Cost Basis	0
Total Past Due	21	20
Muncipal [Member]
Financing Receivable Recorded Investment [Line Items]
2024	175	25
2023	26	83
2022	77	16
2021	12	10
2020	8	1
Prior	71	80
Total Past Due	369	215
Muncipal [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
2024	175	25
2023	26	83
2022	77	15
2021	12	10
2020	8	1
Prior	71	80
Total Past Due	369	214
Muncipal [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
2022	0	1
Total Past Due	0	1
Construction & Development [Member]
Financing Receivable Recorded Investment [Line Items]
2024	675	532
2023	134	317
2022	167	79
2021	56	20
2020	14	9
Prior	8	6
Revolving Loans Amort Cost Basis	1
Total Past Due	1,055	963
Construction & Development [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
2024	667	515
2023	133	311
2022	166	78
2021	55	20
2020	14	9
Prior	8	6
Revolving Loans Amort Cost Basis	1
Total Past Due	1,044	939
Construction & Development [Member] | Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
2024	1	8
2023		2
Total Past Due	1	10
Construction & Development [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
2024	7	9
2023	1	4
2022	1	1
2021	1
Total Past Due	10	14
Farm [Member]
Financing Receivable Recorded Investment [Line Items]
2024	115	101
2023	43	111
2022	76	73
2021	60	29
2020	22	8
Prior	24	23
Total Past Due	340	345
Farm [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
2024	114	101
2023	42	111
2022	72	73
2021	60	24
2020	18	8
Prior	23	22
Total Past Due	329	339
Farm [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
2024	1
2023	1
2022	4
2021	0	5
2020	4
Prior	1	1
Total Past Due	11	6
Non - Owner Occupied CRE [Member]
Financing Receivable Recorded Investment [Line Items]
2024	180	169
2023	90	238
2022	246	175
2021	140	113
2020	65	54
Prior	85	79
Total Past Due	806	828
Non - Owner Occupied CRE [Member] | Charge off [Member]
Financing Receivable Recorded Investment [Line Items]
2023	1
Total Past Due	1
Non - Owner Occupied CRE [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
2024	166	167
2023	86	232
2022	242	172
2021	133	106
2020	58	41
Prior	81	73
Total Past Due	766	791
Non - Owner Occupied CRE [Member] | Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
2024	4
2023	2	5
2022	1	1
2021	1
Prior	1	2
Total Past Due	9	8
Non - Owner Occupied CRE [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
2024	10	2
2023	2	1
2022	3	2
2021	6	7
2020	7	13
Prior	3	4
Total Past Due	31	29
Owner Occupied CRE [Member]
Financing Receivable Recorded Investment [Line Items]
2024	173	158
2023	142	312
2022	305	225
2021	194	114
2020	100	70
Prior	169	158
Total Past Due	1,083	1,037
Owner Occupied CRE [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
2024	170	154
2023	128	305
2022	270	217
2021	177	114
2020	99	62
Prior	160	142
Total Past Due	1,004	994
Owner Occupied CRE [Member] | Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
2024	2	1
2023		1
2022	5	4
2021	7
2020		1
Prior	1	1
Total Past Due	15	8
Owner Occupied CRE [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
2024	1	3
2023	14	6
2022	30	4
2021	10	0
2020	1	7
Prior	8	15
Total Past Due	64	35
Owner Occupied CRE [Member] | Doubtful [Member]
Financing Receivable Recorded Investment [Line Items]
Total Past Due	0
Residential [Member]
Financing Receivable Recorded Investment [Line Items]
2024	612	482
2023	375	421
2022	391	318
2021	273	163
2020	109	70
Prior	246	239
Revolving Loans Amort Cost Basis	190	142
Total Past Due	2,196	1,835
Residential [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
2024	606	477
2023	367	415
2022	378	313
2021	266	158
2020	105	67
Prior	232	229
Revolving Loans Amort Cost Basis	188	138
Total Past Due	2,142	1,797
Residential [Member] | Special Mention [Member]
Financing Receivable Recorded Investment [Line Items]
2024	1	1
2023	1	2
2022	1	2
2021	3	2
Prior	2	3
Revolving Loans Amort Cost Basis	0	1
Total Past Due	8	11
Residential [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
2024	5	4
2023	7	4
2022	12	3
2021	4	3
2020	4	3
Prior	12	7
Revolving Loans Amort Cost Basis	2	3
Total Past Due	46	27
Auto [Member]
Financing Receivable Recorded Investment [Line Items]
2024	339	195
2023	123	213
2022	127	75
2021	39	27
2020	10	10
Prior	2	2
Total Past Due	640	522
Auto [Member] | Charge off [Member]
Financing Receivable Recorded Investment [Line Items]
2023	1	1
2022	1
Total Past Due	2	1
Auto [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
2024	338	195
2023	122	212
2022	126	74
2021	38	26
2020	10	10
Prior	2	2
Total Past Due	636	519
Auto [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
2024	1
2023	1	1
2022	1	1
2021	1	1
Total Past Due	4	3
Non - Auto [Member]
Financing Receivable Recorded Investment [Line Items]
2024	68	72
2023	35	47
2022	26	22
2021	14	4
2020	2	1
Prior	1	1
Revolving Loans Amort Cost Basis	7	7
Total Past Due	153	154
Non - Auto [Member] | Charge off [Member]
Financing Receivable Recorded Investment [Line Items]
2022	1
Total Past Due	1
Non - Auto [Member] | Pass [Member]
Financing Receivable Recorded Investment [Line Items]
2024	68	71
2023	35	47
2022	25	22
2021	14	4
2020	2	1
Prior	1	1
Revolving Loans Amort Cost Basis	7	7
Total Past Due	152	153
Non - Auto [Member] | Substandard [Member]
Financing Receivable Recorded Investment [Line Items]
2024	0	1
2022	1
Total Past Due	$ 1	$ 1