Allowance for Credit Losses and Credit Quality - Recorded Investment by Credit Risk Category (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	$ 34,497,464
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	23,276,341
Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	11,439,602
Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	9,136,870
Commercial | Lease financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	2,699,869
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	11,221,123
Consumer | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	6,179,805
Consumer | Consumer installment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	1,542,411
Consumer | Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	3,498,907
Pass
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	33,603,086
Pass | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	22,469,174
Pass | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	10,930,939
Pass | Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	8,891,361
Pass | Commercial | Lease financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	2,646,874
Pass | Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	11,133,912
Pass | Consumer | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	6,135,096
Pass | Consumer | Consumer installment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	1,541,524
Pass | Consumer | Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	3,457,292
Special Mention
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	514,323
Special Mention | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	513,302
Special Mention | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	315,097
Special Mention | Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	170,114
Special Mention | Commercial | Lease financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	28,091
Special Mention | Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	1,021
Special Mention | Consumer | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	565
Special Mention | Consumer | Consumer installment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	0
Special Mention | Consumer | Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	456
Substandard
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	380,055
Substandard | Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	293,865
Substandard | Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	193,566
Substandard | Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	75,395
Substandard | Commercial | Lease financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	24,904
Substandard | Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	86,190
Substandard | Consumer | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	44,144
Substandard | Consumer | Consumer installment
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	887
Substandard | Consumer | Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Loans and leases	$ 41,159