Loans Held for Investment and Allowance for Credit Losses on Loans - Collateral-dependent Gross Loans Held for Investment by Collateral Type and Related Specific Allocation (Detail) - USD ($) $ in Thousands	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	$ 8,047,448		$ 7,656,645
Specific Allocation	99,626	$ 97,267	96,800	$ 96,920	$ 94,760	$ 92,728
Real Estate Asset [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	23,510		4,240
Business Assets [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	4,541		6,683
Other Assets [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	337		403
Collateral Pledged [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	28,388		11,326
Specific Allocation [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Specific Allocation	6,024		4,152
Real Estate [Member] | Commercial Real Estate Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	954,942		960,944
Specific Allocation	7,370	7,468	7,483	6,808	6,547	6,416
Real Estate [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	1,604,132		1,486,420
Specific Allocation	33,867	33,180	33,080	33,432	32,120	30,190
Real Estate [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	680,807		642,643
Specific Allocation	6,780	6,596	3,950	3,440	3,608	3,778
Real Estate [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	288,900		283,486
Specific Allocation	3,519	3,464	3,414	3,553	3,226	3,275
Real Estate [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	1,335,124		1,258,744
Specific Allocation	5,572	4,923	4,914	4,755	4,454	4,092
Real Estate [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	260,036		244,696
Specific Allocation	1,729	1,652	1,646	1,661	1,444	1,418
Real Estate [Member] | Real Estate Asset [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	643		632
Real Estate [Member] | Real Estate Asset [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	20,142		800
Real Estate [Member] | Real Estate Asset [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	618		638
Real Estate [Member] | Real Estate Asset [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	195		189
Real Estate [Member] | Real Estate Asset [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	79		140
Real Estate [Member] | Real Estate Asset [Member] | Agriculture [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	1,833		1,841
Real Estate [Member] | Business Assets [Member] | Agriculture [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	401		593
Real Estate [Member] | Other Assets [Member] | Agriculture [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	14		15
Real Estate [Member] | Collateral Pledged [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	643		632
Real Estate [Member] | Collateral Pledged [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	20,142		800
Real Estate [Member] | Collateral Pledged [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	618		638
Real Estate [Member] | Collateral Pledged [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	195		189
Real Estate [Member] | Collateral Pledged [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	79		140
Real Estate [Member] | Collateral Pledged [Member] | Agriculture [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	2,248		2,449
Real Estate [Member] | Specific Allocation [Member] | Commercial Real Estate Non-Owner Occupied [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Specific Allocation	250		250
Real Estate [Member] | Specific Allocation [Member] | Construction and Development Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Specific Allocation	2,825		225
Real Estate [Member] | Specific Allocation [Member] | Construction Residential Real Estate Less than 60 Months [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Specific Allocation	134		134
Real Estate [Member] | Specific Allocation [Member] | Residential Real Estate First Lien [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Specific Allocation	66		62
Real Estate [Member] | Specific Allocation [Member] | Residential Real Estate All Other [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Specific Allocation	81		140
Real Estate [Member] | Specific Allocation [Member] | Agriculture [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Specific Allocation	1,193		1,386
Commercial Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	1,436,349		1,289,452
Specific Allocation	21,475	20,482	22,745	25,127	25,079	25,106
Commercial Non-real Estate [Member] | Business Assets [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	4,140		6,090
Commercial Non-real Estate [Member] | Other Assets [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	87		241
Commercial Non-real Estate [Member] | Collateral Pledged [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	4,227		6,331
Commercial Non-real Estate [Member] | Specific Allocation [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Specific Allocation	1,342		1,867
Consumer Non-real Estate [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	469,084		476,467
Specific Allocation	4,383	$ 4,335	4,401	$ 4,344	$ 4,232	$ 4,132
Consumer Non-real Estate [Member] | Other Assets [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	236		147
Consumer Non-real Estate [Member] | Collateral Pledged [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Collateral Dependent Loans	236		147
Consumer Non-real Estate [Member] | Specific Allocation [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Specific Allocation	$ 133		$ 88