Loans (Activity in Allowance for Loan Losses by Portfolio Segment) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Jan. 01, 2020	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	$ 248,666	$ 263,177
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	72,091	73,843	$ 51,593		$ 48,580
Financing Receivable, Credit Loss, Expense (Reversal)	(2,160)	15,156	13,144
Financing Receivable, Allowance for Credit Loss, Writeoff	(5,513)	(18,908)	(14,117)
Financing Receivable, Allowance for Credit Loss, Recovery	5,921	4,739	3,986
Allowance for Loan and Lease Losses Write-offs, Net	408	(14,169)	(10,131)
Commercial Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				$ 21,263
Commercial And Industrial Energy Financing Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	17,217	39,553	37,382		29,052
Financing Receivable, Credit Loss, Expense (Reversal)	(19,207)	85,889	14,388
Financing Receivable, Allowance for Credit Loss, Writeoff	(5,331)	(76,107)	(7,500)
Financing Receivable, Allowance for Credit Loss, Recovery	2,202	2,842	1,442
Allowance for Loan and Lease Losses Write-offs, Net	(3,129)	(73,265)	(6,058)
Commercial And Industrial Energy Financing Receivable [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				(10,453)
Commercial Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	144,936	134,892	31,037		38,777
Financing Receivable, Credit Loss, Expense (Reversal)	8,101	124,427	(6,934)
Financing Receivable, Allowance for Credit Loss, Writeoff	(399)	(7,499)	(1,025)
Financing Receivable, Allowance for Credit Loss, Recovery	2,342	446	219
Allowance for Loan and Lease Losses Write-offs, Net	1,943	(7,053)	(806)
Commercial Real Estate Portfolio Segment [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				(13,519)
Total consumer real estate loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	6,585	7,926	4,113		6,103
Financing Receivable, Credit Loss, Expense (Reversal)	(3,061)	1,906	467
Financing Receivable, Allowance for Credit Loss, Writeoff	(829)	(2,186)	(3,665)
Financing Receivable, Allowance for Credit Loss, Recovery	2,549	1,701	1,208
Allowance for Loan and Lease Losses Write-offs, Net	1,720	(485)	(2,457)
Total consumer real estate loans [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				2,392
Consumer Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	7,837	6,963	8,042		9,620
Financing Receivable, Credit Loss, Expense (Reversal)	10,230	9,632	12,694
Financing Receivable, Allowance for Credit Loss, Writeoff	(18,614)	(17,830)	(24,725)
Financing Receivable, Allowance for Credit Loss, Recovery	9,258	9,367	10,453
Allowance for Loan and Lease Losses Write-offs, Net	(9,356)	(8,463)	(14,272)
Consumer Loan [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				(2,248)
Loans Receivable [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss	248,666	263,177	132,167		$ 132,132
Financing Receivable, Credit Loss, Expense (Reversal)	(6,097)	237,010	33,759
Financing Receivable, Allowance for Credit Loss, Writeoff	(30,686)	(122,530)	(51,032)
Financing Receivable, Allowance for Credit Loss, Recovery	22,272	19,095	17,308
Allowance for Loan and Lease Losses Write-offs, Net	$ (8,414)	$ (103,435)	$ (33,724)
Loans Receivable [Member] | Accounting Standards Update 2016-13 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing Receivable, Allowance for Credit Loss				$ (2,565)