Loans Held for Investment and Allowance for Credit Losses on Loans - Age Analysis of Loans Held for Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	$ 8,047,448	$ 7,656,645
Accruing Loans 90 Days or More Past Due	4,280	9,542
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	954,942	960,944
Accruing Loans 90 Days or More Past Due	532	4,377
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,604,132	1,486,420
Accruing Loans 90 Days or More Past Due	803	913
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	680,807	642,643
Accruing Loans 90 Days or More Past Due	31
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	288,900	283,486
Accruing Loans 90 Days or More Past Due		332
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,335,124	1,258,744
Accruing Loans 90 Days or More Past Due	961	731
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	260,036	244,696
Accruing Loans 90 Days or More Past Due	250	549
Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	432,360	427,139
Accruing Loans 90 Days or More Past Due	916	579
Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,436,349	1,289,452
Accruing Loans 90 Days or More Past Due	587	1,714
Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	469,084	476,467
Accruing Loans 90 Days or More Past Due	200	347
Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	585,714	586,654
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	16,865	16,429
30 to 59 Days Past Due [Member] | Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	3,020	1,386
30 to 59 Days Past Due [Member] | Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	0	2,224
30 to 59 Days Past Due [Member] | Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	405	198
30 to 59 Days Past Due [Member] | Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	229	1,542
30 to 59 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	4,929	3,879
30 to 59 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	866	757
30 to 59 Days Past Due [Member] | Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,805	1,694
30 to 59 Days Past Due [Member] | Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,857	1,501
30 to 59 Days Past Due [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	3,166	3,248
30 to 59 Days Past Due [Member] | Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	588
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	7,069	11,405
60 to 89 Days Past Due [Member] | Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	38	26
60 to 89 Days Past Due [Member] | Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	141	7,371
60 to 89 Days Past Due [Member] | Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,738	158
60 to 89 Days Past Due [Member] | Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	117	206
60 to 89 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,144	1,204
60 to 89 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	152	190
60 to 89 Days Past Due [Member] | Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	937	724
60 to 89 Days Past Due [Member] | Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	831	436
60 to 89 Days Past Due [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	555	1,090
60 to 89 Days Past Due [Member] | Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	416
90 Days and Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	18,407	22,992
90 Days and Greater [Member] | Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	5,379	5,598
90 Days and Greater [Member] | Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,544	1,786
90 Days and Greater [Member] | Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	831	800
90 Days and Greater [Member] | Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	407	405
90 Days and Greater [Member] | Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,213	1,849
90 Days and Greater [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	835	613
90 Days and Greater [Member] | Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,447	1,227
90 Days and Greater [Member] | Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	5,256	10,028
90 Days and Greater [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	495	594
90 Days and Greater [Member] | Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans		92
Past Due Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	42,341	50,826
Past Due Loans [Member] | Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	8,437	7,010
Past Due Loans [Member] | Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,685	11,381
Past Due Loans [Member] | Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	2,974	1,156
Past Due Loans [Member] | Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	753	2,153
Past Due Loans [Member] | Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	9,286	6,932
Past Due Loans [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,853	1,560
Past Due Loans [Member] | Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	4,189	3,645
Past Due Loans [Member] | Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	7,944	11,965
Past Due Loans [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	4,216	4,932
Past Due Loans [Member] | Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,004	92
Current Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	8,005,107	7,605,819
Current Loans [Member] | Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	946,505	953,934
Current Loans [Member] | Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,602,447	1,475,039
Current Loans [Member] | Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	677,833	641,487
Current Loans [Member] | Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	288,147	281,333
Current Loans [Member] | Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,325,838	1,251,812
Current Loans [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	258,183	243,136
Current Loans [Member] | Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	428,171	423,494
Current Loans [Member] | Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	1,428,405	1,277,487
Current Loans [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	464,868	471,535
Current Loans [Member] | Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due Loans	$ 584,710	$ 586,562