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	Dec. 31, 2023	Dec. 31, 2022
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	$ 2,201,950	$ 2,264,479
Fiscal year before current fiscal year	1,564,202	1,428,113
Two years before current fiscal year	1,100,602	752,483
Three years before current fiscal year	560,696	541,762
Four years before current fiscal year	416,738	242,342
Prior	634,924	589,317
Revolving Loans Amortized Cost Basis	1,177,533	1,125,067
Total Loans	7,656,645	6,943,563
Agriculture [Member]
Financing Receivable Recorded Investment [Line Items]
Total Loans	427,139	408,037
Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Total Loans	7,656,645	6,943,563
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	165,315	208,645
Fiscal year before current fiscal year	209,978	181,695
Two years before current fiscal year	156,881	133,825
Three years before current fiscal year	109,088	112,335
Four years before current fiscal year	99,444	53,126
Prior	161,330	151,043
Revolving Loans Amortized Cost Basis	58,908	67,825
Total Loans	960,944	908,494
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	125,041	173,596
Fiscal year before current fiscal year	144,429	145,425
Two years before current fiscal year	124,113	106,285
Three years before current fiscal year	85,619	91,892
Four years before current fiscal year	77,400	44,086
Prior	135,064	119,755
Revolving Loans Amortized Cost Basis	23,004	53,026
Total Loans	714,670	734,065
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	39,735	34,774
Fiscal year before current fiscal year	61,879	34,283
Two years before current fiscal year	28,506	27,153
Three years before current fiscal year	22,473	17,999
Four years before current fiscal year	19,617	8,528
Prior	24,199	29,638
Revolving Loans Amortized Cost Basis	33,304	14,737
Total Loans	229,713	167,112
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	140	235
Fiscal year before current fiscal year	3,580	1,718
Two years before current fiscal year	4,262	387
Three years before current fiscal year	644	1,334
Four years before current fiscal year	1,432	332
Prior	1,051	1,161
Revolving Loans Amortized Cost Basis	2,450	62
Total Loans	13,559	5,229
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	399	40
Fiscal year before current fiscal year	90	269
Three years before current fiscal year	352	1,110
Four years before current fiscal year	656	180
Prior	1,016	489
Revolving Loans Amortized Cost Basis	150
Total Loans	2,663	2,088
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 5 [Member]
Financing Receivable Recorded Investment [Line Items]
Four years before current fiscal year	339
Total Loans	339
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	305,555	472,382
Fiscal year before current fiscal year	418,917	289,942
Two years before current fiscal year	253,559	199,370
Three years before current fiscal year	166,830	157,586
Four years before current fiscal year	126,369	49,058
Prior	141,468	137,512
Revolving Loans Amortized Cost Basis	73,722	77,300
Total Loans	1,486,420	1,383,150
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	221,014	349,333
Fiscal year before current fiscal year	271,637	239,369
Two years before current fiscal year	172,291	170,186
Three years before current fiscal year	113,676	107,983
Four years before current fiscal year	56,831	24,075
Prior	68,576	66,546
Revolving Loans Amortized Cost Basis	44,878	45,372
Total Loans	948,903	1,002,864
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	82,206	115,372
Fiscal year before current fiscal year	139,982	50,573
Two years before current fiscal year	79,204	29,031
Three years before current fiscal year	53,154	46,870
Four years before current fiscal year	63,331	24,877
Prior	72,075	69,601
Revolving Loans Amortized Cost Basis	28,844	31,928
Total Loans	518,796	368,252
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	2,135	7,677
Fiscal year before current fiscal year	6,666
Two years before current fiscal year	1,715	153
Three years before current fiscal year		2,733
Four years before current fiscal year	6,207	64
Prior	251	1,318
Total Loans	16,974	11,945
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	200
Fiscal year before current fiscal year	632
Two years before current fiscal year	349
Four years before current fiscal year		42
Prior	566	47
Total Loans	1,747	89
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	221,407	201,922
Fiscal year before current fiscal year	178,831	112,868
Two years before current fiscal year	94,345	41,406
Three years before current fiscal year	12,688	19,853
Four years before current fiscal year	16,798	4,794
Prior	7,184	5,788
Revolving Loans Amortized Cost Basis	111,390	88,605
Total Loans	642,643	475,236
Real Estate [Member] | Construction and Development Less than 60 Months [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	124,218	164,865
Fiscal year before current fiscal year	133,254	92,595
Two years before current fiscal year	65,472	39,819
Three years before current fiscal year	5,828	5,558
Four years before current fiscal year	3,392	3,146
Prior	5,019	4,993
Revolving Loans Amortized Cost Basis	76,831	40,474
Total Loans	414,014	351,450
Real Estate [Member] | Construction and Development Less than 60 Months [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	95,138	36,090
Fiscal year before current fiscal year	43,884	20,273
Two years before current fiscal year	28,772	1,413
Three years before current fiscal year	6,625	14,248
Four years before current fiscal year	13,406	1,648
Prior	2,146	774
Revolving Loans Amortized Cost Basis	34,559	47,973
Total Loans	224,530	122,419
Real Estate [Member] | Construction and Development Less than 60 Months [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	2,051	967
Fiscal year before current fiscal year	893
Two years before current fiscal year	101	141
Three years before current fiscal year	235
Prior	19	8
Revolving Loans Amortized Cost Basis		158
Total Loans	3,299	1,274
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	800
Two years before current fiscal year		33
Three years before current fiscal year		47
Prior		13
Total Loans	800	93
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	221,463	250,505
Fiscal year before current fiscal year	10,509	13,774
Two years before current fiscal year	1,448	361
Three years before current fiscal year	112	18
Four years before current fiscal year	105
Prior	467	442
Revolving Loans Amortized Cost Basis	49,382	38,205
Total Loans	283,486	303,305
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	158,161	209,699
Fiscal year before current fiscal year	7,551	12,612
Two years before current fiscal year	1,421	259
Three years before current fiscal year	100	18
Four years before current fiscal year	105
Prior	467	42
Revolving Loans Amortized Cost Basis	49,284	36,114
Total Loans	217,089	258,744
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	57,172	39,174
Fiscal year before current fiscal year	2,365	1,152
Two years before current fiscal year	27	102
Three years before current fiscal year	12
Prior		400
Revolving Loans Amortized Cost Basis	98	2,091
Total Loans	59,674	42,919
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	5,457	1,212
Fiscal year before current fiscal year	387
Total Loans	5,844	1,212
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	673	420
Fiscal year before current fiscal year	206	10
Total Loans	879	430
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	348,916	352,115
Fiscal year before current fiscal year	268,012	244,044
Two years before current fiscal year	213,325	168,615
Three years before current fiscal year	141,217	101,339
Four years before current fiscal year	86,027	67,959
Prior	195,200	179,585
Revolving Loans Amortized Cost Basis	6,047	4,242
Total Loans	1,258,744	1,117,899
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	294,363	303,369
Fiscal year before current fiscal year	226,557	205,377
Two years before current fiscal year	174,325	141,752
Three years before current fiscal year	115,055	85,850
Four years before current fiscal year	71,941	55,631
Prior	149,836	136,776
Revolving Loans Amortized Cost Basis	6,047	4,242
Total Loans	1,038,124	932,997
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	51,619	46,751
Fiscal year before current fiscal year	39,146	36,453
Two years before current fiscal year	35,226	25,623
Three years before current fiscal year	24,738	13,414
Four years before current fiscal year	12,591	11,687
Prior	39,264	37,167
Total Loans	202,584	171,095
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	2,175	1,940
Fiscal year before current fiscal year	2,187	1,903
Two years before current fiscal year	2,630	1,065
Three years before current fiscal year	773	1,689
Four years before current fiscal year	1,140	497
Prior	4,009	3,826
Total Loans	12,914	10,920
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	759	55
Fiscal year before current fiscal year	122	311
Two years before current fiscal year	1,144	175
Three years before current fiscal year	651	386
Four years before current fiscal year	355	144
Prior	2,091	1,816
Total Loans	5,122	2,887
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	49,193	37,805
Fiscal year before current fiscal year	30,966	13,103
Two years before current fiscal year	9,994	12,539
Three years before current fiscal year	9,814	7,129
Four years before current fiscal year	5,139	5,084
Prior	15,834	14,611
Revolving Loans Amortized Cost Basis	123,756	105,927
Total Loans	244,696	196,198
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	44,475	31,741
Fiscal year before current fiscal year	24,861	11,012
Two years before current fiscal year	8,381	10,696
Three years before current fiscal year	8,122	5,458
Four years before current fiscal year	3,753	3,607
Prior	12,827	11,198
Revolving Loans Amortized Cost Basis	46,479	41,653
Total Loans	148,898	115,365
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	4,244	5,683
Fiscal year before current fiscal year	5,819	1,887
Two years before current fiscal year	1,415	1,744
Three years before current fiscal year	1,652	1,589
Four years before current fiscal year	1,308	1,237
Prior	2,527	2,574
Revolving Loans Amortized Cost Basis	74,388	62,395
Total Loans	91,353	77,109
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	355	381
Fiscal year before current fiscal year	262	186
Two years before current fiscal year	198	71
Three years before current fiscal year	40	50
Four years before current fiscal year	23	201
Prior	391	786
Revolving Loans Amortized Cost Basis	1,942	1,828
Total Loans	3,211	3,503
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	119
Fiscal year before current fiscal year	24	18
Two years before current fiscal year		28
Three years before current fiscal year		32
Four years before current fiscal year	55	39
Prior	89	53
Revolving Loans Amortized Cost Basis	947	51
Total Loans	1,234	221
Real Estate [Member] | Agriculture [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	91,544	109,168
Fiscal year before current fiscal year	73,848	67,507
Two years before current fiscal year	53,929	49,247
Three years before current fiscal year	39,130	32,862
Four years before current fiscal year	26,736	18,553
Prior	51,498	49,846
Revolving Loans Amortized Cost Basis	90,454	80,854
Total Loans	427,139	408,037
Real Estate [Member] | Agriculture [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	52,934	73,722
Fiscal year before current fiscal year	51,099	44,037
Two years before current fiscal year	34,840	35,684
Three years before current fiscal year	26,603	22,094
Four years before current fiscal year	17,863	12,064
Prior	33,052	31,517
Revolving Loans Amortized Cost Basis	46,981	42,542
Total Loans	263,372	261,660
Real Estate [Member] | Agriculture [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	28,829	28,351
Fiscal year before current fiscal year	20,931	22,773
Two years before current fiscal year	18,245	9,638
Three years before current fiscal year	9,826	10,548
Four years before current fiscal year	8,207	6,025
Prior	15,833	15,233
Revolving Loans Amortized Cost Basis	41,018	33,844
Total Loans	142,889	126,412
Real Estate [Member] | Agriculture [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	9,516	6,435
Fiscal year before current fiscal year	1,185	476
Two years before current fiscal year	789	3,427
Three years before current fiscal year	2,570	140
Four years before current fiscal year	296	320
Prior	2,372	2,703
Revolving Loans Amortized Cost Basis	2,454	4,452
Total Loans	19,182	17,953
Real Estate [Member] | Agriculture [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	265	660
Fiscal year before current fiscal year	633	221
Two years before current fiscal year	55	498
Three years before current fiscal year	131	80
Four years before current fiscal year	370	144
Prior	241	393
Revolving Loans Amortized Cost Basis	1	16
Total Loans	1,696	2,012
Commercial Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	351,089	372,602
Fiscal year before current fiscal year	216,257	252,996
Two years before current fiscal year	180,400	85,651
Three years before current fiscal year	46,483	63,919
Four years before current fiscal year	44,266	31,322
Prior	42,213	45,680
Revolving Loans Amortized Cost Basis	408,744	389,284
Total Loans	1,289,452	1,241,454
Commercial Non-real Estate [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	252,112	282,252
Fiscal year before current fiscal year	176,013	205,516
Two years before current fiscal year	159,470	67,229
Three years before current fiscal year	39,097	50,725
Four years before current fiscal year	36,907	13,780
Prior	33,824	40,989
Revolving Loans Amortized Cost Basis	277,740	280,774
Total Loans	975,163	941,265
Commercial Non-real Estate [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	95,590	88,017
Fiscal year before current fiscal year	35,955	46,604
Two years before current fiscal year	19,519	17,420
Three years before current fiscal year	6,591	11,447
Four years before current fiscal year	6,456	15,628
Prior	8,071	3,582
Revolving Loans Amortized Cost Basis	127,800	105,783
Total Loans	299,982	288,481
Commercial Non-real Estate [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	2,206	2,093
Fiscal year before current fiscal year	2,598	461
Two years before current fiscal year	1,011	346
Three years before current fiscal year	109	738
Four years before current fiscal year	121	1,566
Prior	164	180
Revolving Loans Amortized Cost Basis	1,779	2,544
Total Loans	7,988	7,928
Commercial Non-real Estate [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,181	240
Fiscal year before current fiscal year	1,691	415
Two years before current fiscal year	400	656
Three years before current fiscal year	686	745
Four years before current fiscal year	309	348
Prior	154	929
Revolving Loans Amortized Cost Basis	1,425	183
Total Loans	5,846	3,516
Commercial Non-real Estate [Member] | Grade 5 [Member]
Financing Receivable Recorded Investment [Line Items]
Three years before current fiscal year		264
Four years before current fiscal year	473
Total Loans	473	264
Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	231,415	225,305
Fiscal year before current fiscal year	122,160	115,940
Two years before current fiscal year	63,184	44,216
Three years before current fiscal year	21,034	22,999
Four years before current fiscal year	10,012	7,601
Prior	4,377	3,603
Revolving Loans Amortized Cost Basis	24,285	27,092
Total Loans	476,467	446,756
Consumer Non-real Estate [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	211,028	203,238
Fiscal year before current fiscal year	105,365	104,380
Two years before current fiscal year	55,079	39,779
Three years before current fiscal year	18,529	21,035
Four years before current fiscal year	8,939	6,589
Prior	3,301	2,187
Revolving Loans Amortized Cost Basis	22,184	26,263
Total Loans	424,425	403,471
Consumer Non-real Estate [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	19,085	21,011
Fiscal year before current fiscal year	14,919	10,538
Two years before current fiscal year	6,764	3,978
Three years before current fiscal year	2,062	1,541
Four years before current fiscal year	702	822
Prior	910	1,340
Revolving Loans Amortized Cost Basis	2,085	825
Total Loans	46,527	40,055
Consumer Non-real Estate [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	941	827
Fiscal year before current fiscal year	1,424	671
Two years before current fiscal year	932	405
Three years before current fiscal year	326	282
Four years before current fiscal year	299	134
Prior	156	63
Revolving Loans Amortized Cost Basis	11	4
Total Loans	4,089	2,386
Consumer Non-real Estate [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	361	229
Fiscal year before current fiscal year	452	351
Two years before current fiscal year	409	54
Three years before current fiscal year	117	141
Four years before current fiscal year	72	56
Prior	10	13
Revolving Loans Amortized Cost Basis	5
Total Loans	1,426	844
Oil and Gas [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	216,053	34,030
Fiscal year before current fiscal year	34,724	136,244
Two years before current fiscal year	73,537	17,253
Three years before current fiscal year	14,300	23,722
Four years before current fiscal year	1,842	4,845
Prior	15,353	1,207
Revolving Loans Amortized Cost Basis	230,845	245,733
Total Loans	586,654	463,034
Oil and Gas [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	147,902	24,303
Fiscal year before current fiscal year	29,658	125,209
Two years before current fiscal year	72,127	16,482
Three years before current fiscal year	13,898	682
Four years before current fiscal year	1,553	1,678
Prior	15,015	880
Revolving Loans Amortized Cost Basis	180,321	199,995
Total Loans	460,474	369,229
Oil and Gas [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	66,080	7,610
Fiscal year before current fiscal year	4,851	10,668
Two years before current fiscal year	1,019	766
Three years before current fiscal year	402	23,040
Four years before current fiscal year	279	3,167
Prior	177	327
Revolving Loans Amortized Cost Basis	50,201	45,240
Total Loans	123,009	90,818
Oil and Gas [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,758	2,117
Fiscal year before current fiscal year	132	47
Two years before current fiscal year	225	5
Revolving Loans Amortized Cost Basis	323	498
Total Loans	2,438	2,667
Oil and Gas [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	313
Fiscal year before current fiscal year	83	320
Two years before current fiscal year	166
Four years before current fiscal year	10
Prior	161
Total Loans	$ 733	$ 320