Allowance for Credit Losses and Credit Quality - Recorded Investment by Credit Risk Category (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	$ 7,225,960
Loans and leases		$ 34,497,464
Revolving Loans and Leases Converted to Term Loans and Leases	284,224
Commercial
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	4,172,566
Loans and leases		23,276,341
Revolving Loans and Leases Converted to Term Loans and Leases	228,112
Commercial | Commercial and industrial
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	4,023,501
Loans and leases		11,439,602
Revolving Loans and Leases Converted to Term Loans and Leases	41,938
Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	110,052
Loans and leases		9,136,870
Revolving Loans and Leases Converted to Term Loans and Leases	0
Commercial | Lease financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	39,013
Loans and leases		2,699,869
Revolving Loans and Leases Converted to Term Loans and Leases	186,174
Consumer
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	3,053,394
Loans and leases		11,221,123
Revolving Loans and Leases Converted to Term Loans and Leases	56,112
Consumer | Residential mortgage
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Loans and leases		6,179,805
Revolving Loans and Leases Converted to Term Loans and Leases	16,884
Consumer | Consumer installment
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	32,441
Loans and leases		1,542,411
Revolving Loans and Leases Converted to Term Loans and Leases	73
Consumer | Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	3,020,953
Loans and leases		3,498,907
Revolving Loans and Leases Converted to Term Loans and Leases	39,155
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]
Financing Receivable, Revolving, Converted to Term Loan	3,786,856
Loans and leases		10,930,939
Revolving Loans and Leases Converted to Term Loans and Leases	41,929
Pass | Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	109,791
Loans and leases		8,891,361
Revolving Loans and Leases Converted to Term Loans and Leases	0
Pass | Commercial | Lease financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	34,276
Loans and leases		2,646,874
Revolving Loans and Leases Converted to Term Loans and Leases	176,789
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]
Financing Receivable, Revolving, Converted to Term Loan	0
Loans and leases		6,135,096
Revolving Loans and Leases Converted to Term Loans and Leases	15,799
Pass | Consumer | Consumer installment
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	32,334
Loans and leases		1,541,524
Revolving Loans and Leases Converted to Term Loans and Leases	73
Pass | Consumer | Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	2,981,806
Loans and leases		3,457,292
Revolving Loans and Leases Converted to Term Loans and Leases	37,149
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]
Financing Receivable, Revolving, Converted to Term Loan	129,718
Loans and leases		315,097
Revolving Loans and Leases Converted to Term Loans and Leases	0
Special Mention | Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	261
Loans and leases		170,114
Revolving Loans and Leases Converted to Term Loans and Leases	0
Special Mention | Commercial | Lease financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	3,837
Loans and leases		28,091
Revolving Loans and Leases Converted to Term Loans and Leases	6,173
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]
Financing Receivable, Revolving, Converted to Term Loan	0
Loans and leases		565
Revolving Loans and Leases Converted to Term Loans and Leases	0
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]
Financing Receivable, Revolving, Converted to Term Loan	30
Loans and leases		456
Revolving Loans and Leases Converted to Term Loans and Leases	0
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]
Financing Receivable, Revolving, Converted to Term Loan	106,927
Loans and leases		193,566
Revolving Loans and Leases Converted to Term Loans and Leases	9
Substandard | Commercial | Commercial real estate
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	0
Loans and leases		75,395
Revolving Loans and Leases Converted to Term Loans and Leases	0
Substandard | Commercial | Lease financing
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	900
Loans and leases		24,904
Revolving Loans and Leases Converted to Term Loans and Leases	3,212
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]
Financing Receivable, Revolving, Converted to Term Loan	0
Loans and leases		44,144
Revolving Loans and Leases Converted to Term Loans and Leases	1,085
Substandard | Consumer | Consumer installment
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	107
Loans and leases		887
Revolving Loans and Leases Converted to Term Loans and Leases	0
Substandard | Consumer | Home equity
Financing Receivable, Allowance for Credit Loss [Line Items]
Financing Receivable, Revolving, Converted to Term Loan	39,117
Loans and leases		$ 41,159
Revolving Loans and Leases Converted to Term Loans and Leases	$ 2,006