Loans Held-for-Investment and Allowance for Credit Losses - Schedule of amortized cost basis of loans on nonaccrual status and loans past due over 90 days still accruing (Detail) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	$ 52,129	$ 55,121
Non-accrual loans without a specific ACL	22,619	24,251
Accruing loans past due more than 90 days	218	892
Commercial [Member] \| Commercial and Industrial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	2,645	3,639
Non-accrual loans without a specific ACL	89	110
Accruing loans past due more than 90 days	0	0
Commercial [Member] \| Municipal [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	0	17
Non-accrual loans without a specific ACL	0	0
Accruing loans past due more than 90 days	0	0
Agriculture [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	1,392	1,622
Non-accrual loans without a specific ACL	0	274
Accruing loans past due more than 90 days	0	0
Real Estate [Member] \| Construction & Development [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	1,150	2,644
Non-accrual loans without a specific ACL	0	0
Accruing loans past due more than 90 days	0	404
Real Estate [Member] \| Farm [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	1,944	2,066
Non-accrual loans without a specific ACL	1,741	1,858
Accruing loans past due more than 90 days	0	0
Real Estate [Member] \| Non-Owner Occupied CRE [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	3,217	2,874
Non-accrual loans without a specific ACL	1,649	1,243
Accruing loans past due more than 90 days	0	0
Real Estate [Member] \| Owner Occupied CRE [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	24,645	26,606
Non-accrual loans without a specific ACL	14,872	15,939
Accruing loans past due more than 90 days	0	488
Real Estate [Member] \| Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	16,272	14,558
Non-accrual loans without a specific ACL	4,268	4,827
Accruing loans past due more than 90 days	218	0
Consumer [Member] \| Auto [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	662	871
Non-accrual loans without a specific ACL	0	0
Accruing loans past due more than 90 days	0	0
Consumer [Member] \| Non-Auto [Member]
Loans and Leases Receivable Disclosure [Line Items]
Non-accrual	202	224
Non-accrual loans without a specific ACL	0	0
Accruing loans past due more than 90 days	$ 0	$ 0

Loans Held-for-Investment and Allowance for Credit Losses - Schedule of amortized cost basis of loans on nonaccrual status and loans past due over 90 days still accruing (Detail) - USD ($)
$ in Thousands