Loans - Activity in the Allowance for Credit Losses on Loans by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	$ 227,621
Charge-offs	(4,200)
Ending balance	231,514
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	104,237	$ 72,091
Credit loss, expense (reversal)	(20,684)	17,561
Charge-offs	(6,180)	(3,455)
Recoveries	1,092	829
Net charge-offs	(5,088)	(2,626)
Ending balance	78,465	87,026
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	18,062	17,217
Credit loss, expense (reversal)	966	(2,044)
Charge-offs	0	(371)
Recoveries	163	620
Net charge-offs	163	249
Ending balance	19,191	15,422
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	90,301	144,936
Credit loss, expense (reversal)	25,361	(15,609)
Charge-offs	0	(702)
Recoveries	31	329
Net charge-offs	31	(373)
Ending balance	115,693	128,954
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	8,004	6,585
Credit loss, expense (reversal)	1,283	(26)
Charge-offs	(250)	(231)
Recoveries	671	31
Net charge-offs	421	(200)
Ending balance	9,708	6,359
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	7,017	7,837
Credit loss, expense (reversal)	5,749	4,582
Charge-offs	(6,942)	(5,771)
Recoveries	2,633	2,426
Net charge-offs	(4,309)	(3,345)
Ending balance	8,457	9,074
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	227,621	248,666
Credit loss, expense (reversal)	12,675	4,464
Charge-offs	(13,372)	(10,530)
Recoveries	4,590	4,235
Net charge-offs	(8,782)	(6,295)
Ending balance	$ 231,514	$ 246,835