Asset Quality - Post-Modification Outstanding Recorded Investment by Concession Type for Our Commercial Accruing and Nonaccruing TDRs (Details) - 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 commercial and consumer TDRs	$ 22	$ 18	$ 60	$ 34
Commercial Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Extension of Maturity Date	0	8	26	8
Payment or Covenant Modification/Deferment	16	0	23	0
Bankruptcy Plan Modification	0	0	0	0
Increase in new commitment or new money	0	4	0	4
Total	16	12	49	12
Consumer Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Interest rate reduction	2	1	4	9
Other	4	5	7	13
Total	$ 6	$ 6	$ 11	$ 22