Loans - Activity in the Allowance for Credit Losses on Loans by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance			$ 245,996
Ending balance	$ 263,129		263,129
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	78,554	$ 75,166	74,006	$ 104,237
Credit loss, expense (reversal)	4,697	(623)	13,625	(18,903)
Charge-offs	(3,907)	(943)	(10,333)	(14,259)
Recoveries	1,232	707	3,278	3,232
Net charge-offs	(2,675)	(236)	(7,055)	(11,027)
Ending balance	80,576	74,307	80,576	74,307
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	11,485	14,929	17,814	18,062
Credit loss, expense (reversal)	146	1,784	(6,668)	(1,683)
Charge-offs	0	0	(79)	(518)
Recoveries	490	353	1,054	1,205
Net charge-offs	490	353	975	687
Ending balance	12,121	17,066	12,121	17,066
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	140,020	120,926	130,598	90,301
Credit loss, expense (reversal)	2,791	5,424	12,304	35,918
Charge-offs	0	(62)	(122)	(62)
Recoveries	14	204	45	335
Net charge-offs	14	142	(77)	273
Ending balance	142,825	126,492	142,825	126,492
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	15,707	13,035	13,538	8,004
Credit loss, expense (reversal)	3,838	2,130	7,819	7,235
Charge-offs	(2,013)	(170)	(4,090)	(1,500)
Recoveries	120	44	385	1,300
Net charge-offs	(1,893)	(126)	(3,705)	(200)
Ending balance	17,652	15,039	17,652	15,039
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	10,541	9,563	10,040	7,017
Credit loss, expense (reversal)	4,990	4,893	16,768	15,649
Charge-offs	(8,007)	(8,189)	(24,624)	(22,147)
Recoveries	2,431	3,064	7,771	8,812
Net charge-offs	(5,576)	(5,125)	(16,853)	(13,335)
Ending balance	9,955	9,331	9,955	9,331
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	256,307	233,619	245,996	227,621
Credit loss, expense (reversal)	16,462	13,608	43,848	38,216
Charge-offs	(13,927)	(9,364)	(39,248)	(38,486)
Recoveries	4,287	4,372	12,533	14,884
Net charge-offs	(9,640)	(4,992)	(26,715)	(23,602)
Ending balance	$ 263,129	$ 242,235	$ 263,129	$ 242,235