Loans (Activity in Allowance for Loan Losses by Portfolio Segment) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	$ 270,151
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	281,495	$ 270,151
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	87,569	74,006	$ 104,237
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	19,936	24,494	(16,709)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(12,794)	(14,828)	(18,315)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	3,728	3,897	4,793
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(9,066)	(10,931)	(13,522)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	98,439	87,569	74,006
Commercial And Industrial Energy Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	9,992	17,814	18,062
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	504	(8,977)	(1,067)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	0	(79)	(518)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	1,067	1,234	1,337
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	1,067	1,155	819
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	11,563	9,992	17,814
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	143,205	130,598	90,301
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	(3,486)	16,479	40,889
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(4,639)	(3,919)	(955)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	30	47	363
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(4,609)	(3,872)	(592)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	135,110	143,205	130,598
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	19,106	13,538	8,004
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	10,777	9,753	6,736
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(5,551)	(4,940)	(2,883)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	1,305	755	1,681
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(4,246)	(4,185)	(1,202)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	25,637	19,106	13,538
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	10,279	10,040	7,017
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	16,887	23,083	23,012
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(27,931)	(33,344)	(31,260)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	11,511	10,500	11,271
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(16,420)	(22,844)	(19,989)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	10,746	10,279	10,040
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	270,151	245,996	227,621
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	44,618	64,832	52,861
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(50,915)	(57,110)	(53,931)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	17,641	16,433	19,445
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(33,274)	(40,677)	(34,486)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	$ 281,495	$ 270,151	$ 245,996