Investment Securities (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Mar. 31, 2023
Schedule of Investments [Line Items]
Net unsettled investment purchases	$ 262
Net unsettled investment sales			$ 30
Investment securities, allowance for credit loss	93	$ 92
Pretax loss included in AOCI from derivatives	(289)		$ (305)
Gross gain (loss) on sale of securities	1
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	36,600
Fair value of debt securities of a single issuer that exceeds 10 percent of shareholders equity	33,300
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	31,700
Fair value of debt securities of a single issuer that exceeds 10 percent of shareholders equity	$ 29,100