Loans and Leases (Summary Of Loan And Lease Portfolio Aging By Class Of Loan) (Detail) - USD ($)	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	$ 213,108,000	$ 193,766,000
Financing Receivable, Nonaccrual	173,193,000	151,059,000	$ 151,059,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	198,000	0
Financing Receivable, Not Past Due	21,589,409,000	19,843,220,000
Loans and leases	21,802,517,000	20,036,986,000	19,269,883,000
Financial Asset, 30 to 59 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	26,620,000	28,545,000
Financial Asset, 60 to 89 Days Past Due [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	13,097,000	14,162,000
Commercial Portfolio Segment [Member]
Financing Receivable, Past Due [Line Items]
Financing Receivable, Nonaccrual	91,375,000		76,504,000
Loans and leases	14,754,083,000	12,830,177,000	12,249,888,000
Commercial Portfolio Segment [Member] | Commercial non-mortgage
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	75,052,000	62,080,000
Financing Receivable, Nonaccrual	67,542,000	59,369,000	59,369,000
Financing Receivable, Not Past Due	6,939,355,000	5,234,531,000
Loans and leases	7,014,407,000	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	6,931,000	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	579,000	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	138,000	139,000
Financing Receivable, Nonaccrual	138,000	139,000	139,000
Financing Receivable, Not Past Due	940,386,000	1,046,747,000
Loans and leases	940,524,000	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	18,471,000	13,273,000
Financing Receivable, Nonaccrual	15,902,000	11,563,000	11,563,000
Financing Receivable, Not Past Due	6,188,843,000	5,936,066,000
Loans and leases	6,207,314,000	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	1,206,000	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	1,165,000	454,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	198,000	0
Commercial Portfolio Segment [Member] | 6172 Finance Lessors
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	14,238,000	11,218,000
Financing Receivable, Nonaccrual	7,793,000	5,433,000	5,433,000
Financing Receivable, Not Past Due	577,600,000	526,123,000
Loans and leases	591,838,000	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	5,590,000	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	855,000	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	81,818,000		74,555,000
Loans and leases	7,048,434,000	7,206,809,000	7,019,995,000
Consumer Portfolio Segment [Member] | Residential
Financing Receivable, Past Due [Line Items]
Financing Receivable, Past Due	62,088,000	56,800,000
Financing Receivable, Nonaccrual	46,579,000	43,193,000	43,193,000
Financing Receivable, Not Past Due	4,859,485,000	4,915,885,000
Loans and leases	4,921,573,000	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	7,445,000	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	8,064,000	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	40,389,000	43,988,000
Financing Receivable, Nonaccrual	34,022,000	30,170,000	$ 30,170,000
Financing Receivable, Not Past Due	1,883,624,000	1,970,556,000
Loans and leases	1,924,013,000	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	4,603,000	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	1,764,000	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	2,732,000	6,268,000
Financing Receivable, Nonaccrual	1,217,000	1,192,000
Financing Receivable, Not Past Due	200,116,000	213,312,000
Loans and leases	202,848,000	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	845,000	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	670,000	807,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	$ 0	$ 0