Investments (Repurchase Agreements and Securities Lending Transactions) (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	$ 6,097	$ 6,589
Total cash collateral for loaned securities	5,207	6,100
Overnight & Continuous
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	6,097	6,189
Total cash collateral for loaned securities	4,623	5,622
Up to 30 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	0	200
Total cash collateral for loaned securities	584	478
30 to 90 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	0	200
Total cash collateral for loaned securities	0	0
U.S. Treasury securities and obligations of U.S. government authorities and agencies
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	5,977	6,579
Total cash collateral for loaned securities	1	1
U.S. Treasury securities and obligations of U.S. government authorities and agencies | Overnight & Continuous
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	5,977	6,179
Total cash collateral for loaned securities	1	1
U.S. Treasury securities and obligations of U.S. government authorities and agencies | Up to 30 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	0	200
Total cash collateral for loaned securities	0	0
U.S. Treasury securities and obligations of U.S. government authorities and agencies | 30 to 90 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	0	200
Obligations of U.S. states and their political subdivisions
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	46	61
Obligations of U.S. states and their political subdivisions | Overnight & Continuous
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	46	61
Obligations of U.S. states and their political subdivisions | Up to 30 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	0	0
Foreign government bonds
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	326	299
Foreign government bonds | Overnight & Continuous
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	308	285
Foreign government bonds | Up to 30 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	18	14
U.S. public corporate securities
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	3,886	4,504
U.S. public corporate securities | Overnight & Continuous
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	3,422	4,109
U.S. public corporate securities | Up to 30 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	464	395
Foreign public corporate securities
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	699	875
Foreign public corporate securities | Overnight & Continuous
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	597	806
Foreign public corporate securities | Up to 30 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	102	69
Commercial mortgage-backed securities
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	120	0
Commercial mortgage-backed securities | Overnight & Continuous
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	120	0
Commercial mortgage-backed securities | Up to 30 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	0	0
Commercial mortgage-backed securities | 30 to 90 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	0	0
Residential mortgage-backed securities
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	0	10
Residential mortgage-backed securities | Overnight & Continuous
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	0	10
Residential mortgage-backed securities | Up to 30 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	0	0
Residential mortgage-backed securities | 30 to 90 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total securities sold under agreements to repurchase	0	0
Equity securities
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	249	360
Equity securities | Overnight & Continuous
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	249	360
Equity securities | Up to 30 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Total cash collateral for loaned securities	$ 0	$ 0