Investment Securities (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022	Mar. 31, 2022
Schedule of Investments [Line Items]
Net unsettled investment sales	$ 30
Net unsettled investment purchases			$ 800
Investment securities, allowance for credit loss	148	$ 149
Pretax loss included in AOCI from derivatives	(305)		$ (22)
Federal National Mortgage Association Certificates and Obligations (FNMA)
Schedule of Investments [Line Items]
Debt securities amortized cost amount of debt securities exceeds 10 percent of shareholders equity	39,200
Fair value of debt securities of a single issuer that exceeds 10 percent of shareholders equity	36,600
Federal Home Loan Mortgage Corporation (FHLMC) Insured Loans
Schedule of Investments [Line Items]
Debt securities amortized cost amount of debt securities exceeds 10 percent of shareholders equity	33,000
Fair value of debt securities of a single issuer that exceeds 10 percent of shareholders equity	$ 31,000