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, 2021	Dec. 31, 2020
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	$ 2,297,658	$ 2,702,149
Fiscal year before current fiscal year	1,023,819	1,042,043
Two years before current fiscal year	747,672	619,306
Three years before current fiscal year	372,852	397,399
Four years before current fiscal year	233,568	322,434
Prior	583,158	558,406
Revolving Loans Amortized Cost Basis	910,715	752,769
Total Loans	6,169,442	6,394,506
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	172,286	180,678
Fiscal year before current fiscal year	146,179	139,579
Two years before current fiscal year	120,483	87,398
Three years before current fiscal year	58,745	56,932
Four years before current fiscal year	36,544	53,561
Prior	123,764	118,157
Revolving Loans Amortized Cost Basis	26,738	23,457
Total Loans	684,739	659,762
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	136,757	136,638
Fiscal year before current fiscal year	112,106	107,664
Two years before current fiscal year	97,417	75,262
Three years before current fiscal year	49,642	46,584
Four years before current fiscal year	28,208	37,857
Prior	94,015	89,940
Revolving Loans Amortized Cost Basis	17,669	18,941
Total Loans	535,814	512,886
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	35,192	42,993
Fiscal year before current fiscal year	33,198	31,817
Two years before current fiscal year	21,570	11,060
Three years before current fiscal year	8,397	9,644
Four years before current fiscal year	7,871	14,558
Prior	28,395	25,494
Revolving Loans Amortized Cost Basis	8,682	4,209
Total Loans	143,305	139,775
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year		1,010
Fiscal year before current fiscal year	275	32
Two years before current fiscal year	606	334
Three years before current fiscal year	261	704
Four years before current fiscal year	465	895
Prior	1,028	2,671
Revolving Loans Amortized Cost Basis	62
Total Loans	2,697	5,646
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	337	37
Fiscal year before current fiscal year	600	66
Two years before current fiscal year	890	742
Three years before current fiscal year	445
Four years before current fiscal year		251
Prior	326	52
Revolving Loans Amortized Cost Basis	325	307
Total Loans	2,923	1,455
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	313,768	358,110
Fiscal year before current fiscal year	256,098	225,621
Two years before current fiscal year	168,595	116,377
Three years before current fiscal year	90,446	94,470
Four years before current fiscal year	57,005	94,985
Prior	155,820	123,389
Revolving Loans Amortized Cost Basis	53,592	37,787
Total Loans	1,095,324	1,050,739
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	252,718	282,985
Fiscal year before current fiscal year	204,892	166,369
Two years before current fiscal year	114,429	88,717
Three years before current fiscal year	51,440	72,117
Four years before current fiscal year	37,305	86,190
Prior	118,264	81,749
Revolving Loans Amortized Cost Basis	29,257	31,747
Total Loans	808,305	809,874
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	53,548	62,688
Fiscal year before current fiscal year	51,206	56,026
Two years before current fiscal year	50,912	27,188
Three years before current fiscal year	38,850	20,416
Four years before current fiscal year	19,466	8,755
Prior	36,808	41,492
Revolving Loans Amortized Cost Basis	24,335	5,890
Total Loans	275,125	222,455
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	7,095	7,718
Fiscal year before current fiscal year		3,137
Two years before current fiscal year	3,254	472
Three years before current fiscal year	121	1,937
Four years before current fiscal year	234	40
Prior	656	148
Revolving Loans Amortized Cost Basis		150
Total Loans	11,360	13,602
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	407	4,719
Fiscal year before current fiscal year		89
Three years before current fiscal year	35
Prior	92
Total Loans	534	4,808
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	211,932	138,974
Fiscal year before current fiscal year	41,862	73,928
Two years before current fiscal year	70,946	16,812
Three years before current fiscal year	13,814	5,441
Four years before current fiscal year	2,774	2,491
Prior	4,691	4,364
Revolving Loans Amortized Cost Basis	69,447	33,086
Total Loans	415,466	275,096
Real Estate [Member] | Construction and Development Less than 60 Months [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	173,384	121,699
Fiscal year before current fiscal year	34,351	62,722
Two years before current fiscal year	57,729	12,821
Three years before current fiscal year	9,276	4,655
Four years before current fiscal year	1,953	2,334
Prior	4,181	3,824
Revolving Loans Amortized Cost Basis	32,294	22,288
Total Loans	313,168	230,343
Real Estate [Member] | Construction and Development Less than 60 Months [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	37,275	13,433
Fiscal year before current fiscal year	7,511	11,142
Two years before current fiscal year	13,161	3,973
Three years before current fiscal year	4,526	764
Four years before current fiscal year	803	157
Prior	510	540
Revolving Loans Amortized Cost Basis	37,153	10,798
Total Loans	100,939	40,807
Real Estate [Member] | Construction and Development Less than 60 Months [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,273	3,842
Two years before current fiscal year		9
Three years before current fiscal year	6
Total Loans	1,279	3,851
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		64
Two years before current fiscal year	56	9
Three years before current fiscal year	6	22
Four years before current fiscal year	18
Total Loans	80	95
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	221,959	188,717
Fiscal year before current fiscal year	10,350	4,914
Two years before current fiscal year	41	69
Three years before current fiscal year		21
Four years before current fiscal year	18	33
Prior	454	491
Revolving Loans Amortized Cost Basis	21,702	35,948
Total Loans	254,524	230,193
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	193,311	159,432
Fiscal year before current fiscal year	7,786	4,214
Two years before current fiscal year	41	69
Three years before current fiscal year		21
Four years before current fiscal year	18	33
Prior	29	23
Revolving Loans Amortized Cost Basis	16,247	25,918
Total Loans	217,432	189,710
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	28,170	27,400
Fiscal year before current fiscal year	2,564	580
Prior	425	468
Revolving Loans Amortized Cost Basis	5,455	10,030
Total Loans	36,614	38,478
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	478	1,885
Fiscal year before current fiscal year		120
Total Loans	478	2,005
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	302,129	321,317
Fiscal year before current fiscal year	202,546	163,500
Two years before current fiscal year	117,334	111,135
Three years before current fiscal year	80,738	86,271
Four years before current fiscal year	58,207	65,123
Prior	172,124	179,868
Revolving Loans Amortized Cost Basis	3,928	3,362
Total Loans	937,006	930,576
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	256,834	281,908
Fiscal year before current fiscal year	174,718	140,246
Two years before current fiscal year	99,082	87,317
Three years before current fiscal year	64,949	70,541
Four years before current fiscal year	45,211	50,419
Prior	128,898	138,772
Revolving Loans Amortized Cost Basis	3,928	3,362
Total Loans	773,620	772,565
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	44,080	35,924
Fiscal year before current fiscal year	26,073	20,492
Two years before current fiscal year	15,719	21,965
Three years before current fiscal year	12,612	13,447
Four years before current fiscal year	10,926	12,254
Prior	38,230	34,312
Total Loans	147,640	138,394
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,151	2,754
Fiscal year before current fiscal year	1,266	2,029
Two years before current fiscal year	2,054	1,375
Three years before current fiscal year	1,930	2,073
Four years before current fiscal year	1,155	1,213
Prior	3,523	5,194
Total Loans	11,079	14,638
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	64	731
Fiscal year before current fiscal year	489	733
Two years before current fiscal year	479	478
Three years before current fiscal year	1,247	210
Four years before current fiscal year	915	1,186
Prior	1,473	1,590
Total Loans	4,667	4,928
Real Estate [Member] | Residential Real Estate First Lien [Member] | Grade 5 [Member]
Financing Receivable Recorded Investment [Line Items]
Four years before current fiscal year		51
Total Loans		51
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	18,965	25,774
Fiscal year before current fiscal year	16,539	17,814
Two years before current fiscal year	10,722	13,176
Three years before current fiscal year	7,379	8,707
Four years before current fiscal year	5,710	5,984
Prior	14,981	14,766
Revolving Loans Amortized Cost Basis	86,722	86,662
Total Loans	161,018	172,883
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	16,376	21,492
Fiscal year before current fiscal year	13,320	15,461
Two years before current fiscal year	8,691	11,010
Three years before current fiscal year	5,609	6,717
Four years before current fiscal year	4,101	5,381
Prior	12,386	11,037
Revolving Loans Amortized Cost Basis	30,840	29,851
Total Loans	91,323	100,949
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	2,183	3,694
Fiscal year before current fiscal year	2,941	1,675
Two years before current fiscal year	1,919	1,268
Three years before current fiscal year	1,500	1,809
Four years before current fiscal year	895	450
Prior	2,202	2,793
Revolving Loans Amortized Cost Basis	55,000	56,295
Total Loans	66,640	67,984
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	250	384
Fiscal year before current fiscal year	98	461
Two years before current fiscal year	112	328
Three years before current fiscal year	232	116
Four years before current fiscal year	702	119
Prior	309	221
Revolving Loans Amortized Cost Basis	538	494
Total Loans	2,241	2,123
Real Estate [Member] | Residential Real Estate All Other [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	156	204
Fiscal year before current fiscal year	180	217
Two years before current fiscal year		570
Three years before current fiscal year	38	65
Four years before current fiscal year	12	34
Prior	84	715
Revolving Loans Amortized Cost Basis	344	22
Total Loans	814	1,827
Real Estate [Member] | Farmland [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	68,244	71,116
Fiscal year before current fiscal year	52,318	58,104
Two years before current fiscal year	48,829	29,842
Three years before current fiscal year	21,863	21,563
Four years before current fiscal year	18,140	19,323
Prior	41,766	36,790
Revolving Loans Amortized Cost Basis	21,019	17,592
Total Loans	272,179	254,330
Real Estate [Member] | Farmland [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	47,485	51,284
Fiscal year before current fiscal year	39,216	27,116
Two years before current fiscal year	23,627	18,993
Three years before current fiscal year	15,180	13,821
Four years before current fiscal year	12,579	13,517
Prior	29,457	27,100
Revolving Loans Amortized Cost Basis	6,946	8,185
Total Loans	174,490	160,016
Real Estate [Member] | Farmland [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	16,063	15,737
Fiscal year before current fiscal year	8,702	30,684
Two years before current fiscal year	23,688	6,639
Three years before current fiscal year	5,488	6,391
Four years before current fiscal year	4,159	4,763
Prior	10,848	8,916
Revolving Loans Amortized Cost Basis	10,455	7,140
Total Loans	79,403	80,270
Real Estate [Member] | Farmland [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	3,587	3,681
Fiscal year before current fiscal year	4,021	290
Two years before current fiscal year	1,514	152
Three years before current fiscal year	74	1,055
Four years before current fiscal year	1,293	703
Prior	1,316	551
Revolving Loans Amortized Cost Basis	3,386	1,955
Total Loans	15,191	8,387
Real Estate [Member] | Farmland [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,109	414
Fiscal year before current fiscal year	379	14
Two years before current fiscal year		4,058
Three years before current fiscal year	1,121	296
Four years before current fiscal year	109	340
Prior	145	223
Revolving Loans Amortized Cost Basis	232	312
Total Loans	3,095	5,657
Commercial and Agricultural Non-Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	442,949	308,900
Fiscal year before current fiscal year	135,102	190,171
Two years before current fiscal year	111,281	150,412
Three years before current fiscal year	55,683	85,101
Four years before current fiscal year	32,177	55,151
Prior	56,033	60,950
Revolving Loans Amortized Cost Basis	423,262	343,034
Total Loans	1,256,487	1,193,719
Commercial and Agricultural Non-Real Estate [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	353,164	225,207
Fiscal year before current fiscal year	102,137	146,263
Two years before current fiscal year	83,615	118,571
Three years before current fiscal year	33,943	77,547
Four years before current fiscal year	27,701	46,687
Prior	43,750	37,767
Revolving Loans Amortized Cost Basis	288,745	256,282
Total Loans	933,055	908,324
Commercial and Agricultural Non-Real Estate [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	85,920	64,187
Fiscal year before current fiscal year	30,568	40,901
Two years before current fiscal year	25,097	29,787
Three years before current fiscal year	9,607	6,590
Four years before current fiscal year	2,612	7,054
Prior	10,575	22,710
Revolving Loans Amortized Cost Basis	105,682	73,134
Total Loans	270,061	244,363
Commercial and Agricultural Non-Real Estate [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	2,995	18,922
Fiscal year before current fiscal year	2,185	1,400
Two years before current fiscal year	1,347	1,402
Three years before current fiscal year	11,479	723
Four years before current fiscal year	1,291	271
Prior	599	327
Revolving Loans Amortized Cost Basis	26,642	12,659
Total Loans	46,538	35,704
Commercial and Agricultural Non-Real Estate [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	870	584
Fiscal year before current fiscal year	212	1,607
Two years before current fiscal year	1,222	652
Three years before current fiscal year	654	241
Four years before current fiscal year	573	1,139
Prior	1,109	146
Revolving Loans Amortized Cost Basis	2,193	959
Total Loans	6,833	5,328
Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	222,450	182,645
Fiscal year before current fiscal year	88,564	104,625
Two years before current fiscal year	50,662	46,413
Three years before current fiscal year	20,026	14,269
Four years before current fiscal year	6,639	7,460
Prior	3,429	2,137
Revolving Loans Amortized Cost Basis	21,600	18,715
Total Loans	413,370	376,264
Consumer Non-real Estate [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	201,893	168,544
Fiscal year before current fiscal year	80,616	94,375
Two years before current fiscal year	43,793	41,715
Three years before current fiscal year	17,587	13,157
Four years before current fiscal year	5,723	6,831
Prior	2,048	1,768
Revolving Loans Amortized Cost Basis	20,600	18,132
Total Loans	372,260	344,522
Consumer Non-real Estate [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	19,349	13,444
Fiscal year before current fiscal year	7,551	9,123
Two years before current fiscal year	6,119	4,104
Three years before current fiscal year	2,167	842
Four years before current fiscal year	816	507
Prior	1,342	266
Revolving Loans Amortized Cost Basis	996	574
Total Loans	38,340	28,860
Consumer Non-real Estate [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,146	568
Fiscal year before current fiscal year	307	840
Two years before current fiscal year	551	450
Three years before current fiscal year	203	175
Four years before current fiscal year	86	75
Prior	31	63
Revolving Loans Amortized Cost Basis	4	2
Total Loans	2,328	2,173
Consumer Non-real Estate [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	62	89
Fiscal year before current fiscal year	90	287
Two years before current fiscal year	199	144
Three years before current fiscal year	69	95
Four years before current fiscal year	14	47
Prior	8	40
Revolving Loans Amortized Cost Basis		7
Total Loans	442	709
Oil and Gas [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	212,863	240,492
Fiscal year before current fiscal year	35,874	31,395
Two years before current fiscal year	20,488	21,870
Three years before current fiscal year	3,914	926
Four years before current fiscal year	259	558
Prior	543	4,874
Revolving Loans Amortized Cost Basis	154,967	128,751
Total Loans	428,908	428,866
Oil and Gas [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	188,072	151,000
Fiscal year before current fiscal year	26,090	19,288
Two years before current fiscal year	6,579	15,589
Three years before current fiscal year	1,257	464
Four years before current fiscal year	89	25
Prior	73	4,777
Revolving Loans Amortized Cost Basis	139,687	92,123
Total Loans	361,847	283,266
Oil and Gas [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	17,150	73,882
Fiscal year before current fiscal year	9,774	11,996
Two years before current fiscal year	13,909	6,217
Three years before current fiscal year	2,657	396
Four years before current fiscal year	170	169
Prior	215	81
Revolving Loans Amortized Cost Basis	13,186	34,210
Total Loans	57,061	126,951
Oil and Gas [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	6,641	9,010
Fiscal year before current fiscal year	10	111
Two years before current fiscal year		64
Three years before current fiscal year		66
Four years before current fiscal year		364
Prior	255
Revolving Loans Amortized Cost Basis	2,024	2,418
Total Loans	8,930	12,033
Oil and Gas [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	1,000	6,600
Prior		16
Revolving Loans Amortized Cost Basis	70
Total Loans	1,070	6,616
Other Loans [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	110,113	685,426
Fiscal year before current fiscal year	38,387	32,392
Two years before current fiscal year	28,291	25,802
Three years before current fiscal year	20,244	23,698
Four years before current fiscal year	16,095	17,765
Prior	9,553	12,620
Revolving Loans Amortized Cost Basis	27,738	24,375
Total Loans	250,421	822,078
Other Loans [Member] | Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	109,830	685,426
Fiscal year before current fiscal year	38,379	32,392
Two years before current fiscal year	28,176	25,707
Three years before current fiscal year	20,171	20,638
Four years before current fiscal year	13,908	16,378
Prior	8,425	10,341
Revolving Loans Amortized Cost Basis	26,076	22,976
Total Loans	244,965	813,858
Other Loans [Member] | Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
Current fiscal year	283
Two years before current fiscal year		17
Three years before current fiscal year	73	2,936
Four years before current fiscal year	2,187	1,126
Prior	1,041	2,179
Revolving Loans Amortized Cost Basis	488	692
Total Loans	4,072	6,950
Other Loans [Member] | Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
Two years before current fiscal year		78
Four years before current fiscal year		53
Prior	43	67
Revolving Loans Amortized Cost Basis	1,073	36
Total Loans	1,116	234
Other Loans [Member] | Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
Fiscal year before current fiscal year	8
Two years before current fiscal year	115
Three years before current fiscal year		124
Four years before current fiscal year		208
Prior	44	33
Revolving Loans Amortized Cost Basis	101	671
Total Loans	$ 268	$ 1,036