Loans - Activity in the Allowance for Credit Losses on Loans by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance			$ 227,621
Ending balance	$ 233,619		233,619
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	78,465	$ 87,026	104,237	$ 72,091
Credit loss, expense (reversal)	2,404	942	(18,280)	18,503
Charge-offs	(7,136)	(1,891)	(13,316)	(5,346)
Recoveries	1,433	1,193	2,525	2,022
Net charge-offs	(5,703)	(698)	(10,791)	(3,324)
Ending balance	75,166	87,270	75,166	87,270
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	19,191	15,422	18,062	17,217
Credit loss, expense (reversal)	(4,433)	427	(3,467)	(1,617)
Charge-offs	(518)	0	(518)	(371)
Recoveries	689	418	852	1,038
Net charge-offs	171	418	334	667
Ending balance	14,929	16,267	14,929	16,267
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	115,693	128,954	90,301	144,936
Credit loss, expense (reversal)	5,133	(12,232)	30,494	(27,841)
Charge-offs	0	0	0	(702)
Recoveries	100	384	131	713
Net charge-offs	100	384	131	11
Ending balance	120,926	117,106	120,926	117,106
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	9,708	6,359	8,004	6,585
Credit loss, expense (reversal)	3,822	583	5,105	557
Charge-offs	(1,080)	(131)	(1,330)	(362)
Recoveries	585	43	1,256	74
Net charge-offs	(495)	(88)	(74)	(288)
Ending balance	13,035	6,854	13,035	6,854
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	8,457	9,074	7,017	7,837
Credit loss, expense (reversal)	5,007	5,884	10,756	10,466
Charge-offs	(7,016)	(5,322)	(13,958)	(11,093)
Recoveries	3,115	2,499	5,748	4,925
Net charge-offs	(3,901)	(2,823)	(8,210)	(6,168)
Ending balance	9,563	12,135	9,563	12,135
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	231,514	246,835	227,621	248,666
Credit loss, expense (reversal)	11,933	(4,396)	24,608	68
Charge-offs	(15,750)	(7,344)	(29,122)	(17,874)
Recoveries	5,922	4,537	10,512	8,772
Net charge-offs	(9,828)	(2,807)	(18,610)	(9,102)
Ending balance	$ 233,619	$ 239,632	$ 233,619	$ 239,632