Loans and Related Allowance for Credit Losses (Nonperforming Assets) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Nonperforming Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming loans	$ 2,380	$ 2,180
OREO and foreclosed assets	35	36
Total nonperforming assets	$ 2,415	$ 2,216
Nonperforming loans to total loans	0.74%	0.68%
Nonperforming assets to total loans, OREO and foreclosed assets	0.76%	0.69%
Nonperforming assets to total assets	0.43%	0.39%
Nonperforming loans, without allowance for credit losses	$ 500	$ 500
Total commercial | Nonperforming Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming loans	1,514	1,307
Total consumer | Nonperforming Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonperforming loans	$ 866	$ 873
Unsecured Consumer Loans | Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period of financing receivable past due, writeoff	120 days
Unsecured Consumer Loans | Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period of financing receivable past due, writeoff	180 days