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	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	$ 1,124,047
Fiscal year before current fiscal year	1,658,230
Two years before current fiscal year	1,498,663
Three years before current fiscal year	978,072
Four years before current fiscal year	529,805
Prior	861,507
Revolving Loans Amortized Cost Basis	1,397,124
Total Loans	8,047,448	$ 7,656,645
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	62,479
Fiscal year before current fiscal year	147,224
Two years before current fiscal year	204,593
Three years before current fiscal year	160,011
Four years before current fiscal year	102,000
Prior	226,559
Revolving Loans Amortized Cost Basis	52,076
Total Loans	954,942	960,944
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	39,257
Fiscal year before current fiscal year	104,695
Two years before current fiscal year	151,859
Three years before current fiscal year	111,308
Four years before current fiscal year	78,999
Prior	186,219
Revolving Loans Amortized Cost Basis	25,667
Total Loans	698,004
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	23,094
Fiscal year before current fiscal year	34,818
Two years before current fiscal year	49,139
Three years before current fiscal year	44,044
Four years before current fiscal year	21,710
Prior	34,604
Revolving Loans Amortized Cost Basis	24,187
Total Loans	231,596
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	128
Fiscal year before current fiscal year	7,339
Two years before current fiscal year	3,574
Three years before current fiscal year	4,489
Four years before current fiscal year	939
Prior	4,121
Revolving Loans Amortized Cost Basis	2,100
Total Loans	22,690
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	372
Two years before current fiscal year	21
Three years before current fiscal year	170
Four years before current fiscal year	352
Prior	1,615
Revolving Loans Amortized Cost Basis	122
Total Loans	2,652
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	134,947
Fiscal year before current fiscal year	365,494
Two years before current fiscal year	423,997
Three years before current fiscal year	278,687
Four years before current fiscal year	158,255
Prior	198,537
Revolving Loans Amortized Cost Basis	44,215
Total Loans	1,604,132	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	64,168
Fiscal year before current fiscal year	258,439
Two years before current fiscal year	283,026
Three years before current fiscal year	187,391
Four years before current fiscal year	120,052
Prior	126,177
Revolving Loans Amortized Cost Basis	41,093
Total Loans	1,080,346
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	61,660
Fiscal year before current fiscal year	104,871
Two years before current fiscal year	126,693
Three years before current fiscal year	89,290
Four years before current fiscal year	38,105
Prior	71,591
Revolving Loans Amortized Cost Basis	3,122
Total Loans	495,332
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	8,934
Fiscal year before current fiscal year	141
Two years before current fiscal year	13,635
Three years before current fiscal year	1,690
Prior	245
Total Loans	24,645
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	2,043
Two years before current fiscal year	643
Three years before current fiscal year	316
Four years before current fiscal year	98
Prior	524
Total Loans	3,809
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	117,239
Fiscal year before current fiscal year	196,548
Two years before current fiscal year	209,514
Three years before current fiscal year	42,100
Four years before current fiscal year	11,649
Prior	22,628
Revolving Loans Amortized Cost Basis	81,129
Total Loans	680,807	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	49,830
Fiscal year before current fiscal year	76,166
Two years before current fiscal year	146,196
Three years before current fiscal year	33,350
Four years before current fiscal year	9,848
Prior	7,591
Revolving Loans Amortized Cost Basis	51,139
Total Loans	374,120
Real Estate [Member] | Construction and Development Less than 60 Months [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	64,768
Fiscal year before current fiscal year	118,553
Two years before current fiscal year	62,487
Three years before current fiscal year	8,296
Four years before current fiscal year	1,590
Prior	14,969
Revolving Loans Amortized Cost Basis	10,703
Total Loans	281,366
Real Estate [Member] | Construction and Development Less than 60 Months [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	2,641
Fiscal year before current fiscal year	1,829
Two years before current fiscal year	0
Three years before current fiscal year	354
Four years before current fiscal year	71
Prior	68
Revolving Loans Amortized Cost Basis	19,287
Total Loans	24,250
Real Estate [Member] | Construction and Development Less than 60 Months [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	0
Two years before current fiscal year	831
Three years before current fiscal year	100
Four years before current fiscal year	140
Total Loans	1,071
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	136,723
Fiscal year before current fiscal year	82,742
Two years before current fiscal year	18,575
Three years before current fiscal year	8,177
Four years before current fiscal year	110
Prior	546
Revolving Loans Amortized Cost Basis	42,027
Total Loans	288,900	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	78,419
Fiscal year before current fiscal year	48,981
Two years before current fiscal year	15,922
Three years before current fiscal year	8,162
Four years before current fiscal year	98
Prior	546
Revolving Loans Amortized Cost Basis	30,001
Total Loans	182,129
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	54,233
Fiscal year before current fiscal year	33,153
Two years before current fiscal year	2,447
Three years before current fiscal year	15
Four years before current fiscal year	12
Prior	0
Revolving Loans Amortized Cost Basis	11,630
Total Loans	101,490
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	3,503
Fiscal year before current fiscal year	408
Two years before current fiscal year	0
Three years before current fiscal year	0
Prior	0
Revolving Loans Amortized Cost Basis	396
Total Loans	4,307
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	568
Fiscal year before current fiscal year	200
Two years before current fiscal year	206
Total Loans	974
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	180,475
Fiscal year before current fiscal year	279,820
Two years before current fiscal year	258,826
Three years before current fiscal year	202,783
Four years before current fiscal year	158,845
Prior	248,825
Revolving Loans Amortized Cost Basis	5,550
Total Loans	1,335,124	1,258,744
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	134,305
Fiscal year before current fiscal year	211,033
Two years before current fiscal year	205,048
Three years before current fiscal year	162,128
Four years before current fiscal year	130,865
Prior	192,862
Revolving Loans Amortized Cost Basis	5,031
Total Loans	1,041,272
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	43,810
Fiscal year before current fiscal year	65,488
Two years before current fiscal year	50,368
Three years before current fiscal year	37,025
Four years before current fiscal year	25,620
Prior	48,645
Revolving Loans Amortized Cost Basis	519
Total Loans	271,475
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,453
Fiscal year before current fiscal year	2,576
Two years before current fiscal year	3,098
Three years before current fiscal year	2,835
Four years before current fiscal year	1,821
Prior	5,562
Total Loans	17,345
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	907
Fiscal year before current fiscal year	646
Two years before current fiscal year	312
Three years before current fiscal year	795
Four years before current fiscal year	539
Prior	1,756
Total Loans	4,955
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 5 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	77
Prior	0
Total Loans	77
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	23,361
Fiscal year before current fiscal year	40,041
Two years before current fiscal year	25,668
Three years before current fiscal year	8,029
Four years before current fiscal year	8,953
Prior	17,338
Revolving Loans Amortized Cost Basis	136,646
Total Loans	260,036	244,696
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	18,801
Fiscal year before current fiscal year	34,325
Two years before current fiscal year	21,028
Three years before current fiscal year	6,512
Four years before current fiscal year	7,196
Prior	12,957
Revolving Loans Amortized Cost Basis	54,939
Total Loans	155,758
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	3,804
Fiscal year before current fiscal year	5,198
Two years before current fiscal year	4,467
Three years before current fiscal year	1,341
Four years before current fiscal year	1,462
Prior	3,918
Revolving Loans Amortized Cost Basis	79,266
Total Loans	99,456
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	756
Fiscal year before current fiscal year	344
Two years before current fiscal year	106
Three years before current fiscal year	176
Four years before current fiscal year	295
Prior	437
Revolving Loans Amortized Cost Basis	1,507
Total Loans	3,621
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	174
Two years before current fiscal year	67
Three years before current fiscal year	0
Prior	26
Revolving Loans Amortized Cost Basis	934
Total Loans	1,201
Real Estate [Member] | Agriculture [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	56,745
Fiscal year before current fiscal year	67,532
Two years before current fiscal year	67,447
Three years before current fiscal year	48,874
Four years before current fiscal year	34,957
Prior	69,446
Revolving Loans Amortized Cost Basis	87,359
Total Loans	432,360	427,139
Real Estate [Member] | Agriculture [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	26,725
Fiscal year before current fiscal year	36,340
Two years before current fiscal year	44,928
Three years before current fiscal year	31,695
Four years before current fiscal year	22,757
Prior	46,282
Revolving Loans Amortized Cost Basis	46,588
Total Loans	255,315
Real Estate [Member] | Agriculture [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	23,833
Fiscal year before current fiscal year	21,355
Two years before current fiscal year	20,788
Three years before current fiscal year	16,052
Four years before current fiscal year	9,606
Prior	19,830
Revolving Loans Amortized Cost Basis	39,081
Total Loans	150,545
Real Estate [Member] | Agriculture [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	5,833
Fiscal year before current fiscal year	8,951
Two years before current fiscal year	1,119
Three years before current fiscal year	1,076
Four years before current fiscal year	2,589
Prior	3,072
Revolving Loans Amortized Cost Basis	1,686
Total Loans	24,326
Real Estate [Member] | Agriculture [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	354
Fiscal year before current fiscal year	886
Two years before current fiscal year	612
Three years before current fiscal year	51
Four years before current fiscal year	5
Prior	262
Revolving Loans Amortized Cost Basis	4
Total Loans	2,174
Commercial Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	158,385
Fiscal year before current fiscal year	232,677
Two years before current fiscal year	189,001
Three years before current fiscal year	154,351
Four years before current fiscal year	35,067
Prior	65,587
Revolving Loans Amortized Cost Basis	601,281
Total Loans	1,436,349	1,289,452
Commercial Non-real Estate [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	98,481
Fiscal year before current fiscal year	135,724
Two years before current fiscal year	155,712
Three years before current fiscal year	132,447
Four years before current fiscal year	28,731
Prior	58,159
Revolving Loans Amortized Cost Basis	421,728
Total Loans	1,030,982
Commercial Non-real Estate [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	57,646
Fiscal year before current fiscal year	94,429
Two years before current fiscal year	30,313
Three years before current fiscal year	20,608
Four years before current fiscal year	5,593
Prior	6,885
Revolving Loans Amortized Cost Basis	176,353
Total Loans	391,827
Commercial Non-real Estate [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,471
Fiscal year before current fiscal year	2,160
Two years before current fiscal year	2,183
Three years before current fiscal year	1,035
Four years before current fiscal year	235
Prior	250
Revolving Loans Amortized Cost Basis	2,637
Total Loans	9,971
Commercial Non-real Estate [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	787
Fiscal year before current fiscal year	364
Two years before current fiscal year	793
Three years before current fiscal year	255
Four years before current fiscal year	508
Prior	116
Revolving Loans Amortized Cost Basis	563
Total Loans	3,386
Commercial Non-real Estate [Member] | Grade 5 [Member]
Financing Receivable Recorded Investment [Line Items]
Three years before current fiscal year	6
Prior	177
Total Loans	183
Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	116,415
Fiscal year before current fiscal year	173,458
Two years before current fiscal year	90,190
Three years before current fiscal year	47,920
Four years before current fiscal year	13,644
Prior	8,218
Revolving Loans Amortized Cost Basis	19,239
Total Loans	469,084	476,467
Consumer Non-real Estate [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	105,282
Fiscal year before current fiscal year	153,775
Two years before current fiscal year	77,329
Three years before current fiscal year	40,937
Four years before current fiscal year	11,724
Prior	6,655
Revolving Loans Amortized Cost Basis	12,793
Total Loans	408,495
Consumer Non-real Estate [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	9,876
Fiscal year before current fiscal year	17,288
Two years before current fiscal year	10,906
Three years before current fiscal year	5,582
Four years before current fiscal year	1,542
Prior	1,219
Revolving Loans Amortized Cost Basis	6,427
Total Loans	52,840
Consumer Non-real Estate [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,059
Fiscal year before current fiscal year	1,839
Two years before current fiscal year	1,641
Three years before current fiscal year	1,119
Four years before current fiscal year	274
Prior	276
Revolving Loans Amortized Cost Basis	15
Total Loans	6,223
Consumer Non-real Estate [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	198
Fiscal year before current fiscal year	556
Two years before current fiscal year	314
Three years before current fiscal year	282
Four years before current fiscal year	104
Prior	68
Revolving Loans Amortized Cost Basis	4
Total Loans	1,526
Oil and Gas [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	137,278
Fiscal year before current fiscal year	72,694
Two years before current fiscal year	10,852
Three years before current fiscal year	27,140
Four years before current fiscal year	6,325
Prior	3,823
Revolving Loans Amortized Cost Basis	327,602
Total Loans	585,714	$ 586,654
Oil and Gas [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	76,512
Fiscal year before current fiscal year	63,488
Two years before current fiscal year	5,807
Three years before current fiscal year	26,153
Four years before current fiscal year	5,951
Prior	3,116
Revolving Loans Amortized Cost Basis	269,441
Total Loans	450,468
Oil and Gas [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	60,737
Fiscal year before current fiscal year	9,097
Two years before current fiscal year	5,045
Three years before current fiscal year	677
Four years before current fiscal year	374
Prior	267
Revolving Loans Amortized Cost Basis	58,161
Total Loans	134,358
Oil and Gas [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	29
Fiscal year before current fiscal year	109
Three years before current fiscal year	183
Four years before current fiscal year	0
Total Loans	321
Oil and Gas [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Three years before current fiscal year	127
Prior	440
Total Loans	$ 567