Asset Quality - Post-Modification Outstanding Recorded Investment by Concession Type for Our Commercial Accruing and Nonaccruing TDRs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total commercial and consumer TDRs	$ 15	$ 19	$ 36	$ 48
Commercial Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Extension of Maturity Date	0	0	5	8
Payment or Covenant Modification/Deferment	0	0	7	0
Bankruptcy Plan Modification	0	0	0	0
Increase in new commitment or new money	0	0	0	0
Total	0	0	12	8
Consumer Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Interest rate reduction	3	13	6	22
Other	12	6	18	18
Total	$ 15	$ 19	$ 24	$ 40