Loans Held for Investment and Allowance for Credit Losses on Loans - Age Analysis of Loans Held for Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2025	Dec. 31, 2024	Jun. 30, 2024
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	$ 8,114,488	$ 8,025,110	$ 8,047,448
Accruing Loans 90 Days or More Past Due	7,515	7,739
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	937,426	931,709
Accruing Loans 90 Days or More Past Due	514	569
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,674,229	1,578,483
Accruing Loans 90 Days or More Past Due	0	41
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	684,291	756,662
Accruing Loans 90 Days or More Past Due	16	116
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	235,032	250,373
Accruing Loans 90 Days or More Past Due	0
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,462,758	1,431,265
Accruing Loans 90 Days or More Past Due	2,470	797
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	291,362	275,461
Accruing Loans 90 Days or More Past Due	595	370
Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	447,984	449,190
Accruing Loans 90 Days or More Past Due	620	4,754
Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,427,576	1,363,462
Accruing Loans 90 Days or More Past Due	2,819	356
Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	481,725	478,647
Accruing Loans 90 Days or More Past Due	481	504
Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	472,105	509,858
Accruing Loans 90 Days or More Past Due	0	232
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	21,480	25,401
30 to 59 Days Past Due [Member] | Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	525	2,810
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]
Collateral Dependent Loans	1,691	603
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]
Collateral Dependent Loans	753	317
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]
Collateral Dependent Loans	0	292
30 to 59 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	8,090	9,128
30 to 59 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	865	1,498
30 to 59 Days Past Due [Member] | Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,318	1,569
30 to 59 Days Past Due [Member] | Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	4,496	4,325
30 to 59 Days Past Due [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	2,915	3,748
30 to 59 Days Past Due [Member] | Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	827	1,111
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	7,337	24,535
60 to 89 Days Past Due [Member] | Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	33	273
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]
Collateral Dependent Loans	103	16,871
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]
Collateral Dependent Loans	2,361	351
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]
Collateral Dependent Loans	0	622
60 to 89 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,850	2,118
60 to 89 Days Past Due [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	254	559
60 to 89 Days Past Due [Member] | Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	232	1,357
60 to 89 Days Past Due [Member] | Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	810	1,019
60 to 89 Days Past Due [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,203	907
60 to 89 Days Past Due [Member] | Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	491	458
90 Days and Greater [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	43,864	46,755
90 Days and Greater [Member] | Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	6,750	7,963
90 Days and Greater [Member] | Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	17,844	610
90 Days and Greater [Member] | Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,185	20,327
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]
Collateral Dependent Loans	1,068	616
90 Days and Greater [Member] | Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	4,884	3,332
90 Days and Greater [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	681	828
90 Days and Greater [Member] | Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,632	5,691
90 Days and Greater [Member] | Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	6,821	5,983
90 Days and Greater [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,313	1,173
90 Days and Greater [Member] | Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,686	232
Past Due Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	72,681	96,691
Past Due Loans [Member] | Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	7,308	11,046
Past Due Loans [Member] | Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	19,638	18,084
Past Due Loans [Member] | Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	4,299	20,995
Past Due Loans [Member] | Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,068	1,530
Past Due Loans [Member] | Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	14,824	14,578
Past Due Loans [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,800	2,885
Past Due Loans [Member] | Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	3,182	8,617
Past Due Loans [Member] | Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	12,127	11,327
Past Due Loans [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	5,431	5,828
Past Due Loans [Member] | Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	3,004	1,801
Current Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	8,041,807	7,928,419
Current Loans [Member] | Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	930,118	920,663
Current Loans [Member] | Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,654,591	1,560,399
Current Loans [Member] | Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	679,992	735,667
Current Loans [Member] | Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	233,964	248,843
Current Loans [Member] | Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,447,934	1,416,687
Current Loans [Member] | Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	289,562	272,576
Current Loans [Member] | Real Estate [Member] | Agriculture [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	444,802	440,573
Current Loans [Member] | Commercial Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	1,415,449	1,352,135
Current Loans [Member] | Consumer Non-real Estate [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	476,294	472,819
Current Loans [Member] | Oil and Gas [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Collateral Dependent Loans	$ 469,101	$ 508,057