Loans (Activity in Allowance for Loan Losses by Portfolio Segment) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	$ 245,996
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	270,151	$ 245,996
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	74,006	104,237	$ 72,091
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	24,494	(16,709)	34,479
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(14,828)	(18,315)	(6,575)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	3,897	4,793	4,242
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(10,931)	(13,522)	(2,333)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	87,569	74,006	104,237
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	17,814	18,062	17,217
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	(8,977)	(1,067)	(313)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(79)	(518)	(371)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	1,234	1,337	1,529
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	1,155	819	1,158
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	9,992	17,814	18,062
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	130,598	90,301	144,936
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	16,479	40,889	(54,775)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(3,919)	(955)	(702)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	47	363	842
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(3,872)	(592)	140
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	143,205	130,598	90,301
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	13,538	8,004	6,585
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	9,753	6,736	1,813
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(4,940)	(2,883)	(912)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	755	1,681	518
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(4,185)	(1,202)	(394)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	19,106	13,538	8,004
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	10,040	7,017	7,837
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	23,083	23,012	13,517
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(33,344)	(31,260)	(24,388)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	10,500	11,271	10,051
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(22,844)	(19,989)	(14,337)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	10,279	10,040	7,017
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Beginning Balance	245,996	227,621	248,666
Financing Receivable, Excluding Accrued Interest, Credit Loss Expense (Reversal)	64,832	52,861	(5,279)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff	(57,110)	(53,931)	(32,948)
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Recovery	16,433	19,445	17,182
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Write-offs, Net	(40,677)	(34,486)	(15,766)
Financing Receivable, Allowance for Credit Loss, Excluding Accrued Interest, Ending Balance	$ 270,151	$ 245,996	$ 227,621