Loans Held-for-Investment and Allowance for Credit Losses - Schedule of Loans Held-for-Investment by portfolio segment (Detail) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	$ 8,285,120	$ 8,158,276
Less-allowance for credit losses	(107,918)	(105,536)
Loans, net	8,177,202	8,052,740
Commercial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,534,404	1,458,962
Commercial [Member] \| Commercial & Industrial [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,149,931	1,116,461
Commercial [Member] \| Municipal [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	384,473	342,501
Agriculture [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	77,583	95,776
Real Estate [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	5,778,170	5,724,744
Real Estate [Member] \| Construction & Development [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,169,037	1,157,865
Real Estate [Member] \| Farm [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	329,151	327,625
Real Estate [Member] \| Non-Owner Occupied CRE [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	825,771	832,816
Real Estate [Member] \| Owner Occupied CRE [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	1,132,114	1,120,608
Real Estate [Member] \| Residential [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	2,322,097	2,285,830
Consumer [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	894,963	878,794
Consumer [Member] \| Auto [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	751,283	732,351
Consumer [Member] \| Non-Auto [Member]
Loans and Leases Receivable Disclosure [Line Items]
Total Loans	$ 143,680	$ 146,443