Loans and Related Allowance for Credit Losses (Nonperforming Assets) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Document Period End Date	Sep. 30, 2020
Nonperforming loans	$ 2,085	$ 1,635
OREO and foreclosed assets	67	117
Total nonperforming assets	$ 2,152	$ 1,752
Nonperforming loans to total loans	0.84%	0.68%
Nonperforming assets to total loans, OREO and foreclosed assets	0.86%	0.73%
Nonperforming assets to total assets	0.47%	0.43%
Nonperforming loans, without allowance for credit losses	$ 600
Total commercial
Nonperforming loans	915	$ 501
Total consumer
Nonperforming loans	$ 1,170	$ 1,134