Outstanding Loans and Leases and Allowance for Credit Losses - Credit Card and Other Consumer - TDRs Modified by Program Type (Details) - Credit card and other consumer - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
Carrying Value	$ 95	$ 110
Internal programs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Carrying Value	74	74
External programs
Financing Receivable, Troubled Debt Restructuring [Line Items]
Carrying Value	17	27
Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Carrying Value	$ 4	$ 9