Outstanding Loans and Leases and Allowance for Credit Losses - Consumer Real Estate - Modification Programs (Details) - Consumer real estate - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total modifications	$ 513	$ 121	$ 730	$ 223
Modifications under government programs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total modifications	1	0	3	3
Modifications under proprietary programs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total modifications	479	20	665	59
Loans discharged in Chapter 7 bankruptcy
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total modifications	12	21	22	32
Trial modifications
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total modifications	$ 21	$ 80	$ 40	$ 129