Loans & Leases - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unamortized premiums and discounts, deferred direct loan origination fees and costs, and fair value adjustments	$ 202	$ 202		$ 296
Unearned Income	404	404		479
Loans pledged at the FHLB	16,600	16,600		13,100
Loans pledged at the FRB	48,100	48,100		42,600
Sales type lease - interest income	4	7
Direct financing lease - interest income	22	70
Allowance for loan and lease losses	1,143	1,143	$ 1,115	1,103	$ 1,091	$ 1,077	$ 1,196
Commercial leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan and lease losses	$ 20	$ 20		$ 18