Loans Held for Investment and Allowance for Credit Losses on Loans - Gross Loans Held for Investment by Year of Origination and Internally Assigned Credit Grades (Detail) - USD ($)
$ in Thousands

Loans Held for Investment and Allowance for Credit Losses on Loans - Gross Loans Held for Investment by Year of Origination and Internally Assigned Credit Grades (Detail) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	$ 661,082
Fiscal year before current fiscal year	1,566,876
Two years before current fiscal year	1,351,671
Three years before current fiscal year	1,359,279
Four years before current fiscal year	781,640
Prior	1,093,146
Revolving Loans Amortized Cost Basis	1,280,833
Total Loans	8,094,527	$ 8,025,110	$ 7,781,860
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	39,116
Fiscal year before current fiscal year	126,157
Two years before current fiscal year	148,584
Three years before current fiscal year	187,142
Four years before current fiscal year	142,830
Prior	270,698
Revolving Loans Amortized Cost Basis	23,841
Total Loans	938,368	931,709
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	21,686
Fiscal year before current fiscal year	77,228
Two years before current fiscal year	105,688
Three years before current fiscal year	136,337
Four years before current fiscal year	93,581
Prior	209,640
Revolving Loans Amortized Cost Basis	17,585
Total Loans	661,745
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	16,711
Fiscal year before current fiscal year	33,382
Two years before current fiscal year	32,599
Three years before current fiscal year	47,572
Four years before current fiscal year	46,421
Prior	56,775
Revolving Loans Amortized Cost Basis	5,996
Total Loans	239,456
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	387
Fiscal year before current fiscal year	14,041
Two years before current fiscal year	9,920
Three years before current fiscal year	3,080
Four years before current fiscal year	2,441
Prior	2,010
Revolving Loans Amortized Cost Basis	138
Total Loans	32,017
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	332
Fiscal year before current fiscal year	1,506
Two years before current fiscal year	377
Three years before current fiscal year	153
Four years before current fiscal year	387
Prior	2,273
Revolving Loans Amortized Cost Basis	122
Total Loans	5,150
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	89,408
Fiscal year before current fiscal year	218,242
Two years before current fiscal year	391,320
Three years before current fiscal year	404,647
Four years before current fiscal year	227,837
Prior	261,793
Revolving Loans Amortized Cost Basis	36,961
Total Loans	1,630,208	1,578,483
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	56,154
Fiscal year before current fiscal year	109,497
Two years before current fiscal year	282,664
Three years before current fiscal year	262,068
Four years before current fiscal year	173,442
Prior	176,336
Revolving Loans Amortized Cost Basis	23,464
Total Loans	1,083,625
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	33,254
Fiscal year before current fiscal year	82,361
Two years before current fiscal year	108,531
Three years before current fiscal year	141,844
Four years before current fiscal year	52,448
Prior	83,323
Revolving Loans Amortized Cost Basis	13,497
Total Loans	515,258
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	20,633
Two years before current fiscal year	125
Three years before current fiscal year	735
Prior	30
Total Loans	21,523
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	5,751
Four years before current fiscal year	1,947
Prior	2,104
Total Loans	9,802
Real Estate [Member] \| Construction and Development Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	93,582
Fiscal year before current fiscal year	196,527
Two years before current fiscal year	148,778
Three years before current fiscal year	207,502
Four years before current fiscal year	9,648
Prior	29,821
Revolving Loans Amortized Cost Basis	61,813
Total Loans	747,671	756,662
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	40,297
Fiscal year before current fiscal year	107,456
Two years before current fiscal year	97,643
Three years before current fiscal year	151,160
Four years before current fiscal year	8,330
Prior	14,092
Revolving Loans Amortized Cost Basis	31,049
Total Loans	450,027
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	50,697
Fiscal year before current fiscal year	88,588
Two years before current fiscal year	50,994
Three years before current fiscal year	55,526
Four years before current fiscal year	658
Prior	15,465
Revolving Loans Amortized Cost Basis	11,422
Total Loans	273,350
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	2,588
Fiscal year before current fiscal year	483
Two years before current fiscal year	123
Four years before current fiscal year	352
Prior	128
Total Loans	3,674
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Two years before current fiscal year	18
Three years before current fiscal year	816
Four years before current fiscal year	308
Prior	136
Revolving Loans Amortized Cost Basis	19,342
Total Loans	20,620
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	57,396
Fiscal year before current fiscal year	150,273
Two years before current fiscal year	12,797
Three years before current fiscal year	5,229
Four years before current fiscal year	89
Prior	1,758
Revolving Loans Amortized Cost Basis	20,183
Total Loans	247,725	250,373
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	32,101
Fiscal year before current fiscal year	93,178
Two years before current fiscal year	11,462
Three years before current fiscal year	4,470
Four years before current fiscal year	89
Prior	1,758
Revolving Loans Amortized Cost Basis	4,271
Total Loans	147,329
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	25,058
Fiscal year before current fiscal year	54,685
Two years before current fiscal year	1,218
Three years before current fiscal year	553
Revolving Loans Amortized Cost Basis	15,912
Total Loans	97,426
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	237
Fiscal year before current fiscal year	619
Total Loans	856
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	1,791
Two years before current fiscal year	117
Three years before current fiscal year	206
Total Loans	2,114
Real Estate [Member] \| Residential Real Estate First Lien [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	89,163
Fiscal year before current fiscal year	331,774
Two years before current fiscal year	265,354
Three years before current fiscal year	246,869
Four years before current fiscal year	184,725
Prior	325,365
Revolving Loans Amortized Cost Basis	5,825
Total Loans	1,449,075	1,431,265
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	67,422
Fiscal year before current fiscal year	246,761
Two years before current fiscal year	189,340
Three years before current fiscal year	195,013
Four years before current fiscal year	142,744
Prior	251,378
Revolving Loans Amortized Cost Basis	4,856
Total Loans	1,097,514
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	18,221
Fiscal year before current fiscal year	76,975
Two years before current fiscal year	72,008
Three years before current fiscal year	47,839
Four years before current fiscal year	37,344
Prior	65,901
Revolving Loans Amortized Cost Basis	969
Total Loans	319,257
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	3,520
Fiscal year before current fiscal year	6,168
Two years before current fiscal year	3,204
Three years before current fiscal year	3,401
Four years before current fiscal year	2,707
Prior	6,231
Total Loans	25,231
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	1,870
Two years before current fiscal year	802
Three years before current fiscal year	616
Four years before current fiscal year	1,930
Prior	1,855
Total Loans	7,073
Real Estate [Member] \| Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	8,877
Fiscal year before current fiscal year	44,776
Two years before current fiscal year	30,661
Three years before current fiscal year	22,660
Four years before current fiscal year	6,681
Prior	21,004
Revolving Loans Amortized Cost Basis	147,655
Total Loans	282,314	275,461
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	7,051
Fiscal year before current fiscal year	36,798
Two years before current fiscal year	24,767
Three years before current fiscal year	18,504
Four years before current fiscal year	5,291
Prior	15,416
Revolving Loans Amortized Cost Basis	52,478
Total Loans	160,305
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,250
Fiscal year before current fiscal year	6,992
Two years before current fiscal year	5,255
Three years before current fiscal year	3,783
Four years before current fiscal year	1,219
Prior	4,920
Revolving Loans Amortized Cost Basis	92,263
Total Loans	115,682
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	247
Fiscal year before current fiscal year	918
Two years before current fiscal year	394
Three years before current fiscal year	265
Four years before current fiscal year	171
Prior	482
Revolving Loans Amortized Cost Basis	1,924
Total Loans	4,401
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	329
Fiscal year before current fiscal year	68
Two years before current fiscal year	245
Three years before current fiscal year	108
Prior	186
Revolving Loans Amortized Cost Basis	990
Total Loans	1,926
Real Estate [Member] \| Agriculture [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	34,142
Fiscal year before current fiscal year	74,896
Two years before current fiscal year	61,550
Three years before current fiscal year	57,892
Four years before current fiscal year	40,230
Prior	86,191
Revolving Loans Amortized Cost Basis	101,209
Total Loans	456,110	449,190
Real Estate [Member] \| Agriculture [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	15,224
Fiscal year before current fiscal year	38,758
Two years before current fiscal year	37,016
Three years before current fiscal year	37,398
Four years before current fiscal year	26,324
Prior	56,517
Revolving Loans Amortized Cost Basis	52,148
Total Loans	263,385
Real Estate [Member] \| Agriculture [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	18,495
Fiscal year before current fiscal year	34,417
Two years before current fiscal year	21,982
Three years before current fiscal year	17,310
Four years before current fiscal year	12,002
Prior	24,776
Revolving Loans Amortized Cost Basis	41,465
Total Loans	170,447
Real Estate [Member] \| Agriculture [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	413
Fiscal year before current fiscal year	1,260
Two years before current fiscal year	2,306
Three years before current fiscal year	2,319
Four years before current fiscal year	1,742
Prior	4,501
Revolving Loans Amortized Cost Basis	7,471
Total Loans	20,012
Real Estate [Member] \| Agriculture [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	10
Fiscal year before current fiscal year	461
Two years before current fiscal year	246
Three years before current fiscal year	865
Four years before current fiscal year	162
Prior	397
Revolving Loans Amortized Cost Basis	125
Total Loans	2,266
Commercial Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	86,952
Fiscal year before current fiscal year	213,931
Two years before current fiscal year	163,219
Three years before current fiscal year	162,655
Four years before current fiscal year	122,695
Prior	75,085
Revolving Loans Amortized Cost Basis	527,956
Total Loans	1,352,493	1,363,462
Commercial Non-real Estate [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	53,825
Fiscal year before current fiscal year	126,977
Two years before current fiscal year	90,837
Three years before current fiscal year	132,250
Four years before current fiscal year	106,919
Prior	66,222
Revolving Loans Amortized Cost Basis	282,164
Total Loans	859,194
Commercial Non-real Estate [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	32,121
Fiscal year before current fiscal year	84,894
Two years before current fiscal year	69,514
Three years before current fiscal year	28,032
Four years before current fiscal year	15,275
Prior	7,963
Revolving Loans Amortized Cost Basis	208,939
Total Loans	446,738
Commercial Non-real Estate [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	447
Fiscal year before current fiscal year	1,391
Two years before current fiscal year	1,652
Three years before current fiscal year	1,701
Four years before current fiscal year	371
Prior	347
Revolving Loans Amortized Cost Basis	36,508
Total Loans	42,417
Commercial Non-real Estate [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	559
Fiscal year before current fiscal year	669
Two years before current fiscal year	1,212
Three years before current fiscal year	601
Four years before current fiscal year	124
Prior	381
Revolving Loans Amortized Cost Basis	345
Total Loans	3,891
Commercial Non-real Estate [Member] \| Grade 5 [Member]
Financing Receivable Recorded Investment [Line Items]
Two years before current fiscal year	4
Three years before current fiscal year	71
Four years before current fiscal year	6
Prior	172
Total Loans	253
Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	55,602
Fiscal year before current fiscal year	185,171
Two years before current fiscal year	111,773
Three years before current fiscal year	56,385
Four years before current fiscal year	25,060
Prior	10,465
Revolving Loans Amortized Cost Basis	34,456
Total Loans	478,912	478,647
Consumer Non-real Estate [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	48,308
Fiscal year before current fiscal year	165,238
Two years before current fiscal year	94,651
Three years before current fiscal year	46,454
Four years before current fiscal year	20,379
Prior	8,293
Revolving Loans Amortized Cost Basis	21,697
Total Loans	405,020
Consumer Non-real Estate [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	5,231
Fiscal year before current fiscal year	17,991
Two years before current fiscal year	14,393
Three years before current fiscal year	8,298
Four years before current fiscal year	3,716
Prior	1,625
Revolving Loans Amortized Cost Basis	12,744
Total Loans	63,998
Consumer Non-real Estate [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	248
Fiscal year before current fiscal year	1,409
Two years before current fiscal year	2,135
Three years before current fiscal year	1,119
Four years before current fiscal year	742
Prior	401
Revolving Loans Amortized Cost Basis	13
Total Loans	6,067
Consumer Non-real Estate [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,815
Fiscal year before current fiscal year	533
Two years before current fiscal year	594
Three years before current fiscal year	514
Four years before current fiscal year	223
Prior	146
Revolving Loans Amortized Cost Basis	2
Total Loans	3,827
Oil and Gas [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	106,844
Fiscal year before current fiscal year	25,129
Two years before current fiscal year	17,635
Three years before current fiscal year	8,298
Four years before current fiscal year	21,845
Prior	10,966
Revolving Loans Amortized Cost Basis	320,934
Total Loans	511,651	$ 509,858
Oil and Gas [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	73,126
Fiscal year before current fiscal year	15,712
Two years before current fiscal year	10,877
Three years before current fiscal year	4,130
Four years before current fiscal year	20,084
Prior	8,089
Revolving Loans Amortized Cost Basis	223,596
Total Loans	355,614
Oil and Gas [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	33,690
Fiscal year before current fiscal year	9,395
Two years before current fiscal year	6,677
Three years before current fiscal year	4,168
Four years before current fiscal year	1,538
Prior	2,413
Revolving Loans Amortized Cost Basis	96,888
Total Loans	154,769
Oil and Gas [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	28
Fiscal year before current fiscal year	22
Two years before current fiscal year	81
Four years before current fiscal year	165
Prior	56
Revolving Loans Amortized Cost Basis	450
Total Loans	802
Oil and Gas [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Four years before current fiscal year	58
Prior	408
Total Loans	$ 466