Loans - Activity in the Allowance for Credit Losses on Loans by Portfolio Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	$ 245,996
Ending balance	250,297
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	74,006	$ 104,237
Credit loss, expense (reversal)	1,992	(20,684)
Charge-offs	(2,144)	(6,180)
Recoveries	1,742	1,092
Net charge-offs	(402)	(5,088)
Ending balance	75,596	78,465
Commercial and Industrial Total Energy Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	17,814	18,062
Credit loss, expense (reversal)	(3,776)	966
Charge-offs	0	0
Recoveries	180	163
Net charge-offs	180	163
Ending balance	14,218	19,191
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	130,598	90,301
Credit loss, expense (reversal)	7,610	25,361
Charge-offs	0	0
Recoveries	16	31
Net charge-offs	16	31
Ending balance	138,224	115,693
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	13,538	8,004
Credit loss, expense (reversal)	1,806	1,283
Charge-offs	(1,669)	(250)
Recoveries	182	671
Net charge-offs	(1,487)	421
Ending balance	13,857	9,708
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	10,040	7,017
Credit loss, expense (reversal)	4,018	5,749
Charge-offs	(8,257)	(6,942)
Recoveries	2,601	2,633
Net charge-offs	(5,656)	(4,309)
Ending balance	8,402	8,457
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Beginning balance	245,996	227,621
Credit loss, expense (reversal)	11,650	12,675
Charge-offs	(12,070)	(13,372)
Recoveries	4,721	4,590
Net charge-offs	(7,349)	(8,782)
Ending balance	$ 250,297	$ 231,514