Derivatives (Estimated Fair Value of Derivative Assets and Liabilities after Master Netting Agreements and Cash Collateral) (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset Excluding Accruals	$ 8,918	$ 11,577
Derivative Liability, Fair Value, Gross Liability Excluding Accruals	6,307	6,975
Net amount of derivative assets after application of master netting agreements and cash collateral	183	175
Net amount of derivative liabilities after application of master netting agreements and cash collateral	19	25
Over the Counter [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset Excluding Accruals	8,749	11,438
Derivative Liability, Fair Value, Gross Liability Excluding Accruals	6,014	6,628
Derivative Liability, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset	(3,568)	(4,579)
Derivative Asset, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset	(3,568)	(4,579)
Cash collateral on derivative assets	(3,448)	(5,432)
Cash collateral on derivative liabilities	0	0
Securities collateral on derivative assets	(1,563)	(1,322)
Securities collateral on derivative liabilities	(2,427)	(2,024)
Exchange Traded [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset Excluding Accruals	11	18
Derivative Liability, Fair Value, Gross Liability Excluding Accruals	16	5
Gross estimated fair value of derivative assets	1	1
Gross estimated fair value of derivative liabilities	1	1
Cash collateral on derivative assets	0	0
Cash collateral on derivative liabilities	(5)	(3)
Securities collateral on derivative assets	0	0
Securities collateral on derivative liabilities	(10)	(1)
Cleared [Member]
Offsetting Assets [Line Items]
Derivative Asset, Fair Value, Gross Asset Excluding Accruals	158	121
Derivative Liability, Fair Value, Gross Liability Excluding Accruals	277	342
Derivative Liability, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset	(5)	(33)
Derivative Asset, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset	(5)	(33)
Cash collateral on derivative assets	(150)	(35)
Cash collateral on derivative liabilities	(239)	(295)
Securities collateral on derivative assets	0	0
Securities collateral on derivative liabilities	$ (33)	$ (14)