Loans & Leases (Loans and Leases - Additional Information) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unamortized premiums and discounts, deferred loan fees and costs, and fair value adjustments	$ 249	$ 296
Unearned Income	354	479
Loans pledged at the FHLB	16,700	13,100
Loans pledged at the FRB	47,300	42,600
Sales type lease - interest income	13
Direct financing lease - interest income	88
Allowance for loan and lease losses	1,202	1,103	$ 1,196	$ 1,253
Commercial Leases
Accounts, Notes, Loans and Financing Receivable [Line Items]
Allowance for loan and lease losses	$ 17	$ 18