Allowance for Loan and Lease Losses and Credit Quality - Recorded Investment by Credit Risk Category (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	$ 34,497,464	$ 19,073,020
Commercial
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	23,276,341	11,659,108
Commercial | Commercial and industrial
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	11,439,602	6,298,240
Commercial | Commercial real estate
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	9,136,870	2,830,705
Commercial | Lease financing
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	2,699,869	2,530,163
Consumer Loan Portfolio
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	11,221,123	7,413,912
Consumer Loan Portfolio | Residential mortgage
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	6,179,805	2,335,835
Consumer Loan Portfolio | Consumer installment
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	1,542,411	2,003,572
Consumer Loan Portfolio | Home equity
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	3,498,907	3,074,505
Pass
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	33,603,086	18,626,268
Pass | Commercial
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	22,469,174	11,306,388
Pass | Commercial | Commercial and industrial
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	10,930,939	6,033,321
Pass | Commercial | Commercial real estate
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	8,891,361	2,792,103
Pass | Commercial | Lease financing
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	2,646,874	2,480,964
Pass | Consumer Loan Portfolio
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	11,133,912	7,319,880
Pass | Consumer Loan Portfolio | Residential mortgage
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	6,135,096	2,294,740
Pass | Consumer Loan Portfolio | Consumer installment
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	1,541,524	1,981,844
Pass | Consumer Loan Portfolio | Home equity
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	3,457,292	3,043,296
Special Mention
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	514,323	205,010
Special Mention | Commercial
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	513,302	196,355
Special Mention | Commercial | Commercial and industrial
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	315,097	158,296
Special Mention | Commercial | Commercial real estate
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	170,114	12,864
Special Mention | Commercial | Lease financing
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	28,091	25,195
Special Mention | Consumer Loan Portfolio
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	1,021	8,655
Special Mention | Consumer Loan Portfolio | Residential mortgage
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	565	3,606
Special Mention | Consumer Loan Portfolio | Consumer installment
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	0	1,302
Special Mention | Consumer Loan Portfolio | Home equity
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	456	3,747
Substandard
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	380,055	241,742
Substandard | Commercial
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	293,865	156,365
Substandard | Commercial | Commercial and industrial
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	193,566	106,623
Substandard | Commercial | Commercial real estate
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	75,395	25,738
Substandard | Commercial | Lease financing
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	24,904	24,004
Substandard | Consumer Loan Portfolio
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	86,190	85,377
Substandard | Consumer Loan Portfolio | Residential mortgage
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	44,144	37,489
Substandard | Consumer Loan Portfolio | Consumer installment
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	887	20,426
Substandard | Consumer Loan Portfolio | Home equity
Allowance for loan and lease losses, other credit loss reserves
Loans and leases	$ 41,159	$ 27,462