Loans - Activity in the Allowance for Credit Losses on Loans by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	$ 281,495
Ending Balance	286,215
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	98,439	$ 87,569
Credit loss expense (benefit)	2,479	10,181
Charge-offs	(3,697)	(4,336)
Recoveries	1,667	893
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(2,030)	(3,443)
Ending Balance	98,888	94,307
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	11,563	9,992
Credit loss expense (benefit)	(749)	(38)
Charge-offs	0	(52)
Recoveries	268	354
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	268	302
Ending Balance	11,082	10,256
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	135,110	143,205
Credit loss expense (benefit)	2,927	1,970
Charge-offs	0	(2,000)
Recoveries	5	2
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	5	(1,998)
Ending Balance	138,042	143,177
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	25,637	19,106
Credit loss expense (benefit)	2,712	429
Charge-offs	(1,252)	(958)
Recoveries	297	347
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(955)	(611)
Ending Balance	27,394	18,924
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	10,746	10,279
Credit loss expense (benefit)	3,092	2,486
Charge-offs	(6,370)	(6,844)
Recoveries	3,341	2,903
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(3,029)	(3,941)
Ending Balance	10,809	8,824
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning Balance	281,495	270,151
Credit loss expense (benefit)	10,461	15,028
Charge-offs	(11,319)	(14,190)
Recoveries	5,578	4,499
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(5,741)	(9,691)
Ending Balance	$ 286,215	$ 275,488