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, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance			$ 248,666
Ending balance	$ 234,315		234,315
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	87,270	$ 65,271	72,091	$ 73,843
Credit loss, expense (reversal)	10,844	(1,020)	29,347	(8,886)
Charge-offs	(572)	(1,611)	(5,918)	(4,485)
Recoveries	1,288	1,126	3,310	3,294
Net charge-offs	716	(485)	(2,608)	(1,191)
Ending balance	98,830	63,766	98,830	63,766
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	16,267	28,010	17,217	39,553
Credit loss, expense (reversal)	2,491	(7,720)	874	(19,048)
Charge-offs	0	0	(371)	(1,433)
Recoveries	93	159	1,131	1,377
Net charge-offs	93	159	760	(56)
Ending balance	18,851	20,449	18,851	20,449
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	117,106	147,993	144,936	134,892
Credit loss, expense (reversal)	(16,522)	4,007	(44,363)	16,583
Charge-offs	0	0	(702)	(137)
Recoveries	23	54	736	716
Net charge-offs	23	54	34	579
Ending balance	100,607	152,054	100,607	152,054
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	6,854	6,154	6,585	7,926
Credit loss, expense (reversal)	940	(982)	1,497	(3,093)
Charge-offs	(68)	0	(430)	(672)
Recoveries	309	857	383	1,868
Net charge-offs	241	857	(47)	1,196
Ending balance	8,035	6,029	8,035	6,029
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	12,135	7,860	7,837	6,963
Credit loss, expense (reversal)	(216)	2,692	10,250	7,042
Charge-offs	(6,549)	(5,073)	(17,642)	(13,015)
Recoveries	2,622	2,373	7,547	6,862
Net charge-offs	(3,927)	(2,700)	(10,095)	(6,153)
Ending balance	7,992	7,852	7,992	7,852
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	239,632	255,288	248,666	263,177
Credit loss, expense (reversal)	(2,463)	(3,023)	(2,395)	(7,402)
Charge-offs	(7,189)	(6,684)	(25,063)	(19,742)
Recoveries	4,335	4,569	13,107	14,117
Net charge-offs	(2,854)	(2,115)	(11,956)	(5,625)
Ending balance	$ 234,315	$ 250,150	$ 234,315	$ 250,150