Loans and Leases (Summary Of Loan And Lease Portfolio Aging By Class Of Loan) (Detail) - USD ($)	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 184,475,000	$ 193,766,000
Financing Receivable, Nonaccrual	162,676,000	151,059,000	$ 151,059,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Financing Receivable, Not Past Due	21,667,548,000	19,843,220,000
Loans and leases	21,852,023,000	20,036,986,000	19,551,646,000
Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	12,267,000	28,545,000
Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	9,532,000	14,162,000
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	87,590,000		76,504,000
Loans and leases	14,920,116,000	12,830,177,000	12,407,968,000
Commercial Portfolio Segment [Member] | Commercial non-mortgage
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	68,943,000	62,080,000
Financing Receivable, Nonaccrual	67,849,000	59,369,000	59,369,000
Financing Receivable, Not Past Due	7,055,422,000	5,234,531,000
Loans and leases	7,124,365,000	5,296,611,000
Commercial Portfolio Segment [Member] | Commercial non-mortgage | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,027,000	2,094,000
Commercial Portfolio Segment [Member] | Commercial non-mortgage | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	67,000	617,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Commercial Portfolio Segment [Member] | Asset-based
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	3,760,000	139,000
Financing Receivable, Nonaccrual	3,760,000	139,000	139,000
Financing Receivable, Not Past Due	885,951,000	1,046,747,000
Loans and leases	889,711,000	1,046,886,000
Commercial Portfolio Segment [Member] | Asset-based | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Commercial Portfolio Segment [Member] | Asset-based | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	0
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Commercial Portfolio Segment [Member] | Commercial real estate
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	9,129,000	13,273,000
Financing Receivable, Nonaccrual	8,799,000	11,563,000	11,563,000
Financing Receivable, Not Past Due	6,298,438,000	5,936,066,000
Loans and leases	6,307,567,000	5,949,339,000
Commercial Portfolio Segment [Member] | Commercial real estate | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	330,000	1,256,000
Commercial Portfolio Segment [Member] | Commercial real estate | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	0	454,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Commercial Portfolio Segment [Member] | 6172 Finance Lessors
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	9,915,000	11,218,000
Financing Receivable, Nonaccrual	7,182,000	5,433,000	5,433,000
Financing Receivable, Not Past Due	588,558,000	526,123,000
Loans and leases	598,473,000	537,341,000
Commercial Portfolio Segment [Member] | 6172 Finance Lessors | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	183,000	5,493,000
Commercial Portfolio Segment [Member] | 6172 Finance Lessors | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	2,550,000	292,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Consumer Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	75,086,000		74,555,000
Loans and leases	6,931,907,000	7,206,809,000	7,143,678,000
Consumer Portfolio Segment [Member] | Residential
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	50,819,000	56,800,000
Financing Receivable, Nonaccrual	41,554,000	43,193,000	43,193,000
Financing Receivable, Not Past Due	4,835,002,000	4,915,885,000
Loans and leases	4,885,821,000	4,972,685,000
Consumer Portfolio Segment [Member] | Residential | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	4,478,000	7,166,000
Consumer Portfolio Segment [Member] | Residential | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	4,787,000	6,441,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Consumer Portfolio Segment [Member] | Home equity
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	39,605,000	43,988,000
Financing Receivable, Nonaccrual	32,853,000	30,170,000	$ 30,170,000
Financing Receivable, Not Past Due	1,828,364,000	1,970,556,000
Loans and leases	1,867,969,000	2,014,544,000
Consumer Portfolio Segment [Member] | Home equity | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	5,180,000	8,267,000
Consumer Portfolio Segment [Member] | Home equity | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,572,000	5,551,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	0	0
Consumer Portfolio Segment [Member] | Other consumer
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	2,304,000	6,268,000
Financing Receivable, Nonaccrual	679,000	1,192,000
Financing Receivable, Not Past Due	175,813,000	213,312,000
Loans and leases	178,117,000	219,580,000
Consumer Portfolio Segment [Member] | Other consumer | Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	1,069,000	4,269,000
Consumer Portfolio Segment [Member] | Other consumer | Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	556,000	807,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 0