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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Total commercial and consumer TDRs	$ 19	$ 20	$ 48	$ 57
Commercial Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Extension of Maturity Date	0	6	8	11
Payment or Covenant Modification/Deferment	0	0	0	1
Bankruptcy Plan Modification	0	0	0	0
Increase in new commitment or new money	0	2	0	12
Total	0	8	8	24
Consumer Loans
Financing Receivable, Troubled Debt Restructuring [Line Items]
Interest rate reduction	13	4	22	12
Other	6	8	18	21
Total	$ 19	$ 12	$ 40	$ 33