Derivatives (Estimated Fair Value of Derivatives Assets and Liabilities after Master Netting Agreements and Cash Collateral) (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Offsetting Derivative Assets [Abstract]
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	$ 2,719	$ 2,295
Derivative Asset, Not Offset, Policy Election Deduction	(2,028)	(1,659)
Derivative Asset, Collateral, Obligation to Return Cash, Offset	(672)	(629)
Derivative Asset, Fair Value, Amount Offset Against Collateral	19	7
Derivative Asset, Collateral, Obligation to Return Securities, Offset	(6)	(5)
Derivative Asset, Fair Value, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election	13	2
Offsetting Derivative Liabilities [Abstract]
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	5,214	3,910
Derivative Liability, Not Offset, Policy Election Deduction	(2,028)	(1,659)
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0	0
Derivative Liability, Fair Value, Amount Offset Against Collateral	3,186	2,251
Derivative Liability, Collateral, Right to Reclaim Securities, Offset	(3,186)	(2,251)
Derivative Liability, Fair Value, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election	$ 0	$ 0