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, 2021	Dec. 31, 2020
Financing Receivable Recorded Investment [Line Items]
2021	$ 1,538,093
2020	1,378,175
2019	900,281
2018	469,620
2017	358,467
Prior	789,747
Revolving Loans Amortized Cost Basis	756,847
Total Loans	6,191,230	$ 6,394,506
Pegasus Bank [Member]
Financing Receivable Recorded Investment [Line Items]
2021	91,154
2020	101,981
2019	76,339
2018	17,839
2017	37,580
Prior	59,149
Revolving Loans Amortized Cost Basis	202,001
Total Loans	586,043	554,548
Pegasus Bank [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	64,138
2020	87,556
2019	58,223
2018	7,261
2017	16,202
Prior	52,432
Revolving Loans Amortized Cost Basis	153,260
Total Loans	439,072
Pegasus Bank [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	27,016
2020	14,313
2019	18,116
2018	10,578
2017	21,378
Prior	6,717
Revolving Loans Amortized Cost Basis	48,741
Total Loans	146,859
Pegasus Bank [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2020	112
Total Loans	112
Real Estate [Member] \| Pegasus Bank [Member]
Financing Receivable Recorded Investment [Line Items]
Total Loans	297,000
Real Estate [Member] \| Farmland [Member]
Financing Receivable Recorded Investment [Line Items]
2021	38,174
2020	58,949
2019	53,242
2018	27,564
2017	20,478
Prior	50,251
Revolving Loans Amortized Cost Basis	20,350
Total Loans	269,008	252,958
Real Estate [Member] \| Farmland [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	26,621
2020	46,638
2019	25,418
2018	18,375
2017	13,983
Prior	35,431
Revolving Loans Amortized Cost Basis	7,521
Total Loans	173,987
Real Estate [Member] \| Farmland [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	8,767
2020	9,048
2019	26,148
2018	5,702
2017	5,457
Prior	13,424
Revolving Loans Amortized Cost Basis	10,709
Total Loans	79,255
Real Estate [Member] \| Farmland [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	2,786
2020	2,068
2019	1,676
2018	300
2017	742
Prior	1,213
Revolving Loans Amortized Cost Basis	1,842
Total Loans	10,627
Real Estate [Member] \| Farmland [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
2020	1,195
2018	3,187
2017	296
Prior	183
Revolving Loans Amortized Cost Basis	278
Total Loans	5,139
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
2021	84,033
2020	177,604
2019	114,445
2018	65,059
2017	47,147
Prior	156,524
Revolving Loans Amortized Cost Basis	16,718
Total Loans	661,530	641,987
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	66,327
2020	135,671
2019	83,146
2018	53,559
2017	36,961
Prior	112,760
Revolving Loans Amortized Cost Basis	11,507
Total Loans	499,931
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	17,354
2020	38,028
2019	30,351
2018	10,695
2017	9,710
Prior	40,707
Revolving Loans Amortized Cost Basis	4,904
Total Loans	151,749
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	3
2020	3,905
2019	27
2018	266
2017	476
Prior	2,621
Total Loans	7,298
Real Estate [Member] \| Commercial Real Estate Owner Occupied [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	349
2019	921
2018	539
Prior	436
Revolving Loans Amortized Cost Basis	307
Total Loans	2,552
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Recorded Investment [Line Items]
2021	119,058
2020	286,843
2019	195,492
2018	100,282
2017	82,366
Prior	182,838
Revolving Loans Amortized Cost Basis	22,681
Total Loans	989,560	971,158
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	95,260
2020	227,302
2019	147,192
2018	62,169
2017	61,402
Prior	137,491
Revolving Loans Amortized Cost Basis	18,024
Total Loans	748,840
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	16,345
2020	59,541
2019	44,838
2018	37,862
2017	19,357
Prior	43,884
Revolving Loans Amortized Cost Basis	4,657
Total Loans	226,484
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	7,453
2019	3,412
2018	214
2017	1,607
Prior	865
Total Loans	13,551
Real Estate [Member] \| Commercial Real Estate Non-Owner Occupied [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
2019	50
2018	37
Prior	598
Total Loans	685
Real Estate [Member] \| Construction and Development Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
2021	105,475
2020	77,646
2019	79,558
2018	13,583
2017	4,378
Prior	3,983
Revolving Loans Amortized Cost Basis	12,582
Total Loans	297,205	229,615
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	91,143
2020	63,018
2019	66,976
2018	11,381
2017	2,547
Prior	3,210
Revolving Loans Amortized Cost Basis	10,454
Total Loans	248,729
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	12,579
2020	12,938
2019	12,391
2018	2,187
2017	1,811
Prior	773
Revolving Loans Amortized Cost Basis	2,128
Total Loans	44,807
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	1,753
2020	1,690
2019	130
2018	7
Total Loans	3,580
Real Estate [Member] \| Construction and Development Less than 60 Months [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
2019	61
2018	8
2017	20
Total Loans	89
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Recorded Investment [Line Items]
2021	116,210
2020	84,088
2019	52
2018	109
2017	20
Prior	467
Revolving Loans Amortized Cost Basis	7,264
Total Loans	208,210	206,195
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	101,482
2020	69,169
2019	52
2017	20
Prior	30
Revolving Loans Amortized Cost Basis	7,264
Total Loans	178,017
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	14,182
2020	14,919
2018	109
Prior	437
Total Loans	29,647
Real Estate [Member] \| Construction Residential Real Estate Less than 60 Months [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	546
Total Loans	546
Real Estate [Member] \| Residential Real Estate First Lien [Member]
Financing Receivable Recorded Investment [Line Items]
2021	158,602
2020	215,971
2019	128,689
2018	91,194
2017	66,588
Prior	204,513
Total Loans	865,557	853,316
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	134,782
2020	188,553
2019	109,336
2018	69,907
2017	54,107
Prior	154,974
Total Loans	711,659
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	22,669
2020	25,098
2019	16,385
2018	19,237
2017	10,187
Prior	42,381
Total Loans	135,957
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	1,102
2020	1,809
2019	2,526
2018	901
2017	1,360
Prior	4,832
Total Loans	12,530
Real Estate [Member] \| Residential Real Estate First Lien [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	49
2020	511
2019	442
2018	1,149
2017	934
Prior	2,326
Total Loans	5,411
Real Estate [Member] \| Residential Real Estate All Other [Member]
Financing Receivable Recorded Investment [Line Items]
2021	10,879
2020	20,042
2019	13,292
2018	10,161
2017	7,027
Prior	18,671
Revolving Loans Amortized Cost Basis	83,218
Total Loans	163,290	168,081
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	9,847
2020	16,428
2019	11,139
2018	8,009
2017	5,157
Prior	15,276
Revolving Loans Amortized Cost Basis	28,321
Total Loans	94,177
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	746
2020	3,263
2019	1,743
2018	1,325
2017	1,137
Prior	2,367
Revolving Loans Amortized Cost Basis	53,510
Total Loans	64,091
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	272
2020	140
2019	410
2018	248
2017	718
Prior	376
Revolving Loans Amortized Cost Basis	1,042
Total Loans	3,206
Real Estate [Member] \| Residential Real Estate All Other [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	14
2020	211
2018	579
2017	15
Prior	652
Revolving Loans Amortized Cost Basis	345
Total Loans	1,816
Commercial and Agricultural Non-Real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
2021	234,753
2020	190,487
2019	138,512
2018	88,880
2017	61,121
Prior	75,793
Revolving Loans Amortized Cost Basis	316,231
Total Loans	1,105,777	1,159,810
Commercial and Agricultural Non-Real Estate [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	190,653
2020	135,726
2019	105,770
2018	64,491
2017	54,567
Prior	54,870
Revolving Loans Amortized Cost Basis	220,348
Total Loans	826,425
Commercial and Agricultural Non-Real Estate [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	38,938
2020	47,478
2019	29,481
2018	11,780
2017	3,885
Prior	18,985
Revolving Loans Amortized Cost Basis	68,353
Total Loans	218,900
Commercial and Agricultural Non-Real Estate [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	4,900
2020	5,500
2019	1,706
2018	12,010
2017	1,858
Prior	639
Revolving Loans Amortized Cost Basis	21,708
Total Loans	48,321
Commercial and Agricultural Non-Real Estate [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	262
2020	1,783
2019	1,555
2018	599
2017	811
Prior	1,299
Revolving Loans Amortized Cost Basis	5,822
Total Loans	12,131
Consumer Non-real Estate [Member]
Financing Receivable Recorded Investment [Line Items]
2021	119,776
2020	126,346
2019	70,593
2018	30,822
2017	10,769
Prior	5,873
Revolving Loans Amortized Cost Basis	7,378
Total Loans	371,557	355,405
Consumer Non-real Estate [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	110,171
2020	116,215
2019	64,985
2018	27,641
2017	9,497
Prior	4,018
Revolving Loans Amortized Cost Basis	7,084
Total Loans	339,611
Consumer Non-real Estate [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	9,362
2020	9,659
2019	4,641
2018	2,833
2017	1,099
Prior	1,653
Revolving Loans Amortized Cost Basis	287
Total Loans	29,534
Consumer Non-real Estate [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	229
2020	405
2019	787
2018	290
2017	154
Prior	147
Revolving Loans Amortized Cost Basis	3
Total Loans	2,015
Consumer Non-real Estate [Member] \| Grade 4 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	14
2020	67
2019	180
2018	58
2017	19
Prior	55
Revolving Loans Amortized Cost Basis	4
Total Loans	397
Oil and Gas [Member]
Financing Receivable Recorded Investment [Line Items]
2021	80,264
2020	3,462
2019	128
2018	66
Prior	3,444
Revolving Loans Amortized Cost Basis	43,095
Total Loans	130,459	179,355
Oil and Gas [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	53,326
2020	115
2019	59
2018	66
Prior	3,444
Revolving Loans Amortized Cost Basis	33,676
Total Loans	90,686
Oil and Gas [Member] \| Grade 2 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	10,051
2020	3,347
2019	69
Revolving Loans Amortized Cost Basis	9,419
Total Loans	22,886
Oil and Gas [Member] \| Grade 3 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	16,887
Total Loans	16,887
Other Loans [Member]
Financing Receivable Recorded Investment [Line Items]
2021	379,715
2020	34,756
2019	29,939
2018	24,061
2017	20,993
Prior	28,241
Revolving Loans Amortized Cost Basis	25,329
Total Loans	543,034	$ 822,078
Other Loans [Member] \| Grade 1 [Member]
Financing Receivable Recorded Investment [Line Items]
2021	379,715
2020	34,608
2019	29,464
2018	24,034
2017	18,060
Prior	25,568
Revolving Loans Amortized Cost Basis	23,298

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