Loans and Related Allowance for Credit Losses (Nonperforming Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Financing receivable, nonaccrual, no allowance	$ 800
Nonperforming
Total nonperforming loans	2,286	$ 1,635
OREO and Foreclosed Assets	51	117
Total nonperforming assets	$ 2,337	$ 1,752
Nonperforming loans to total loans	0.94%	0.68%
Nonperforming assets to total loans, OREO and foreclosed assets	0.97%	0.73%
Nonperforming assets to total assets	0.50%	0.43%
Minimum
Threshold period of financing receivable past due, writeoff	120 days
Maximum
Threshold period of financing receivable past due, writeoff	180 days
Commercial | Nonperforming
Total nonperforming loans	$ 923	$ 501
Consumer | Nonperforming
Total nonperforming loans	$ 1,363	$ 1,134