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	Sep. 30, 2024	Dec. 31, 2023
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	$ 1,571,555
Fiscal year before current fiscal year	1,563,086
Two years before current fiscal year	1,481,000
Three years before current fiscal year	917,997
Four years before current fiscal year	478,564
Prior	812,951
Revolving Loans Amortized Cost Basis	1,355,208
Total Loans	8,180,361	$ 7,656,645
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	97,908
Fiscal year before current fiscal year	145,325
Two years before current fiscal year	201,569
Three years before current fiscal year	155,082
Four years before current fiscal year	99,653
Prior	215,938
Revolving Loans Amortized Cost Basis	24,045
Total Loans	939,520	960,944
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	57,484
Fiscal year before current fiscal year	100,209
Two years before current fiscal year	148,898
Three years before current fiscal year	102,563
Four years before current fiscal year	77,151
Prior	175,433
Revolving Loans Amortized Cost Basis	18,792
Total Loans	680,530
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	25,814
Fiscal year before current fiscal year	37,446
Two years before current fiscal year	48,964
Three years before current fiscal year	47,874
Four years before current fiscal year	21,235
Prior	35,911
Revolving Loans Amortized Cost Basis	4,971
Total Loans	222,215
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	12,960
Fiscal year before current fiscal year	7,293
Two years before current fiscal year	3,687
Three years before current fiscal year	4,596
Four years before current fiscal year	915
Prior	2,609
Revolving Loans Amortized Cost Basis	160
Total Loans	32,220
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,650
Fiscal year before current fiscal year	377
Two years before current fiscal year	20
Three years before current fiscal year	49
Four years before current fiscal year	352
Prior	1,985
Revolving Loans Amortized Cost Basis	122
Total Loans	4,555
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	177,141
Fiscal year before current fiscal year	376,972
Two years before current fiscal year	424,019
Three years before current fiscal year	270,684
Four years before current fiscal year	149,132
Prior	189,827
Revolving Loans Amortized Cost Basis	44,697
Total Loans	1,632,472	1,486,420
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	74,870
Fiscal year before current fiscal year	271,096
Two years before current fiscal year	280,887
Three years before current fiscal year	187,555
Four years before current fiscal year	119,241
Prior	122,367
Revolving Loans Amortized Cost Basis	40,695
Total Loans	1,096,711
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	91,056
Fiscal year before current fiscal year	105,735
Two years before current fiscal year	129,516
Three years before current fiscal year	81,139
Four years before current fiscal year	29,760
Prior	64,675
Revolving Loans Amortized Cost Basis	4,002
Total Loans	505,883
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	11,030
Two years before current fiscal year	13,616
Three years before current fiscal year	1,686
Four years before current fiscal year	33
Prior	243
Total Loans	26,608
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	185
Fiscal year before current fiscal year	141
Two years before current fiscal year	0
Three years before current fiscal year	304
Four years before current fiscal year	98
Prior	2,542
Revolving Loans Amortized Cost Basis	0
Total Loans	3,270
Real Estate [Member] \| Construction and Development Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	158,231
Fiscal year before current fiscal year	195,693
Two years before current fiscal year	233,537
Three years before current fiscal year	32,148
Four years before current fiscal year	10,813
Prior	21,971
Revolving Loans Amortized Cost Basis	60,745
Total Loans	713,138	642,643
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	74,367
Fiscal year before current fiscal year	79,181
Two years before current fiscal year	171,801
Three years before current fiscal year	30,183
Four years before current fiscal year	9,039
Prior	7,416
Revolving Loans Amortized Cost Basis	29,490
Total Loans	401,477
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	79,077
Fiscal year before current fiscal year	116,406
Two years before current fiscal year	60,905
Three years before current fiscal year	1,202
Four years before current fiscal year	1,567
Prior	14,489
Revolving Loans Amortized Cost Basis	11,913
Total Loans	285,559
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	4,736
Fiscal year before current fiscal year	88
Three years before current fiscal year	663
Four years before current fiscal year	69
Prior	66
Total Loans	5,622
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	51
Fiscal year before current fiscal year	18
Two years before current fiscal year	831
Three years before current fiscal year	100
Four years before current fiscal year	138
Revolving Loans Amortized Cost Basis	19,342
Total Loans	20,480
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	176,803
Fiscal year before current fiscal year	51,346
Two years before current fiscal year	6,631
Three years before current fiscal year	100
Four years before current fiscal year	1,296
Prior	532
Revolving Loans Amortized Cost Basis	25,393
Total Loans	262,101	283,486
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	104,772
Fiscal year before current fiscal year	35,253
Two years before current fiscal year	3,954
Three years before current fiscal year	91
Four years before current fiscal year	1,284
Prior	532
Revolving Loans Amortized Cost Basis	10,942
Total Loans	156,828
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	66,604
Fiscal year before current fiscal year	15,903
Two years before current fiscal year	2,471
Three years before current fiscal year	9
Four years before current fiscal year	12
Prior	0
Revolving Loans Amortized Cost Basis	14,451
Total Loans	99,450
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	4,916
Fiscal year before current fiscal year	0
Two years before current fiscal year	0
Three years before current fiscal year	0
Prior	0
Revolving Loans Amortized Cost Basis	0
Total Loans	4,916
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	511
Fiscal year before current fiscal year	190
Two years before current fiscal year	206
Total Loans	907
Real Estate [Member] \| Residential Real Estate First Lien [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	274,900
Fiscal year before current fiscal year	295,099
Two years before current fiscal year	261,267
Three years before current fiscal year	197,396
Four years before current fiscal year	129,212
Prior	235,334
Revolving Loans Amortized Cost Basis	1,955
Total Loans	1,395,163	1,258,744
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	213,294
Fiscal year before current fiscal year	220,298
Two years before current fiscal year	208,733
Three years before current fiscal year	157,011
Four years before current fiscal year	101,934
Prior	181,950
Revolving Loans Amortized Cost Basis	986
Total Loans	1,084,206
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	55,742
Fiscal year before current fiscal year	70,183
Two years before current fiscal year	49,081
Three years before current fiscal year	35,708
Four years before current fiscal year	24,668
Prior	46,015
Revolving Loans Amortized Cost Basis	969
Total Loans	282,366
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	4,640
Fiscal year before current fiscal year	3,918
Two years before current fiscal year	3,005
Three years before current fiscal year	2,897
Four years before current fiscal year	2,157
Prior	5,635
Total Loans	22,252
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,224
Fiscal year before current fiscal year	700
Two years before current fiscal year	448
Three years before current fiscal year	1,780
Four years before current fiscal year	453
Prior	1,734
Total Loans	6,339
Real Estate [Member] \| Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	37,539
Fiscal year before current fiscal year	36,686
Two years before current fiscal year	25,255
Three years before current fiscal year	7,509
Four years before current fiscal year	8,592
Prior	15,678
Revolving Loans Amortized Cost Basis	140,339
Total Loans	271,598	244,696
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	31,285
Fiscal year before current fiscal year	31,220
Two years before current fiscal year	20,562
Three years before current fiscal year	5,993
Four years before current fiscal year	6,922
Prior	11,298
Revolving Loans Amortized Cost Basis	55,518
Total Loans	162,798
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	5,421
Fiscal year before current fiscal year	4,896
Two years before current fiscal year	4,417
Three years before current fiscal year	1,342
Four years before current fiscal year	1,331
Prior	3,762
Revolving Loans Amortized Cost Basis	82,285
Total Loans	103,454
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	571
Fiscal year before current fiscal year	401
Two years before current fiscal year	226
Three years before current fiscal year	174
Four years before current fiscal year	197
Prior	594
Revolving Loans Amortized Cost Basis	1,629
Total Loans	3,792
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	262
Fiscal year before current fiscal year	169
Two years before current fiscal year	50
Three years before current fiscal year	0
Four years before current fiscal year	142
Prior	24
Revolving Loans Amortized Cost Basis	907
Total Loans	1,554
Real Estate [Member] \| Agriculture [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	65,299
Fiscal year before current fiscal year	73,789
Two years before current fiscal year	63,886
Three years before current fiscal year	46,022
Four years before current fiscal year	33,574
Prior	65,076
Revolving Loans Amortized Cost Basis	80,366
Total Loans	428,012	427,139
Real Estate [Member] \| Agriculture [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	36,702
Fiscal year before current fiscal year	45,768
Two years before current fiscal year	41,775
Three years before current fiscal year	29,706
Four years before current fiscal year	21,769
Prior	43,550
Revolving Loans Amortized Cost Basis	42,446
Total Loans	261,716
Real Estate [Member] \| Agriculture [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	25,454
Fiscal year before current fiscal year	19,370
Two years before current fiscal year	19,784
Three years before current fiscal year	14,665
Four years before current fiscal year	9,183
Prior	18,189
Revolving Loans Amortized Cost Basis	35,079
Total Loans	141,724
Real Estate [Member] \| Agriculture [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	2,497
Fiscal year before current fiscal year	8,160
Two years before current fiscal year	1,503
Three years before current fiscal year	1,481
Four years before current fiscal year	2,548
Prior	3,085
Revolving Loans Amortized Cost Basis	2,744
Total Loans	22,018
Real Estate [Member] \| Agriculture [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	646
Fiscal year before current fiscal year	491
Two years before current fiscal year	824
Three years before current fiscal year	170
Four years before current fiscal year	74
Prior	252
Revolving Loans Amortized Cost Basis	97
Total Loans	2,554
Commercial Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	223,998
Fiscal year before current fiscal year	214,725
Two years before current fiscal year	177,562
Three years before current fiscal year	144,159
Four years before current fiscal year	30,163
Prior	59,449
Revolving Loans Amortized Cost Basis	632,418
Total Loans	1,482,474	1,289,452
Commercial Non-real Estate [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	124,981
Fiscal year before current fiscal year	127,161
Two years before current fiscal year	142,229
Three years before current fiscal year	122,786
Four years before current fiscal year	24,896
Prior	52,512
Revolving Loans Amortized Cost Basis	426,523
Total Loans	1,021,088
Commercial Non-real Estate [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	96,479
Fiscal year before current fiscal year	84,077
Two years before current fiscal year	32,323
Three years before current fiscal year	20,523
Four years before current fiscal year	4,708
Prior	6,396
Revolving Loans Amortized Cost Basis	202,912
Total Loans	447,418
Commercial Non-real Estate [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,647
Fiscal year before current fiscal year	3,005
Two years before current fiscal year	2,292
Three years before current fiscal year	599
Four years before current fiscal year	126
Prior	282
Revolving Loans Amortized Cost Basis	2,438
Total Loans	10,389
Commercial Non-real Estate [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	891
Fiscal year before current fiscal year	482
Two years before current fiscal year	647
Three years before current fiscal year	245
Four years before current fiscal year	432
Prior	89
Revolving Loans Amortized Cost Basis	545
Total Loans	3,331
Commercial Non-real Estate [Member] \| Grade 5 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	0
Two years before current fiscal year	71
Three years before current fiscal year	6
Four years before current fiscal year	1
Prior	170
Total Loans	248
Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	171,011
Fiscal year before current fiscal year	149,348
Two years before current fiscal year	77,329
Three years before current fiscal year	40,219
Four years before current fiscal year	10,796
Prior	6,053
Revolving Loans Amortized Cost Basis	21,719
Total Loans	476,475	476,467
Consumer Non-real Estate [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	154,137
Fiscal year before current fiscal year	130,104
Two years before current fiscal year	65,270
Three years before current fiscal year	34,106
Four years before current fiscal year	9,199
Prior	4,752
Revolving Loans Amortized Cost Basis	11,574
Total Loans	409,142
Consumer Non-real Estate [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	15,183
Fiscal year before current fiscal year	16,368
Two years before current fiscal year	10,112
Three years before current fiscal year	4,926
Four years before current fiscal year	1,227
Prior	1,002
Revolving Loans Amortized Cost Basis	10,128
Total Loans	58,946
Consumer Non-real Estate [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,460
Fiscal year before current fiscal year	2,134
Two years before current fiscal year	1,529
Three years before current fiscal year	917
Four years before current fiscal year	275
Prior	241
Revolving Loans Amortized Cost Basis	15
Total Loans	6,571
Consumer Non-real Estate [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	231
Fiscal year before current fiscal year	720
Two years before current fiscal year	418
Three years before current fiscal year	270
Four years before current fiscal year	95
Prior	58
Revolving Loans Amortized Cost Basis	2
Total Loans	1,794
Consumer Non-real Estate [Member] \| Grade 5 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	22
Prior	0
Total Loans	22
Oil and Gas [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	188,725
Fiscal year before current fiscal year	24,103
Two years before current fiscal year	9,945
Three years before current fiscal year	24,678
Four years before current fiscal year	5,333
Prior	3,093
Revolving Loans Amortized Cost Basis	323,531
Total Loans	579,408	$ 586,654
Oil and Gas [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	77,698
Fiscal year before current fiscal year	15,998
Two years before current fiscal year	5,293
Three years before current fiscal year	23,811
Four years before current fiscal year	4,967
Prior	2,427
Revolving Loans Amortized Cost Basis	232,703
Total Loans	362,897
Oil and Gas [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	110,739
Fiscal year before current fiscal year	7,652
Two years before current fiscal year	4,652
Three years before current fiscal year	584
Four years before current fiscal year	366
Prior	244
Revolving Loans Amortized Cost Basis	90,353
Total Loans	214,590
Oil and Gas [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	288
Fiscal year before current fiscal year	453
Three years before current fiscal year	173
Revolving Loans Amortized Cost Basis	475
Total Loans	1,389
Oil and Gas [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Three years before current fiscal year	110

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