Fair Value Measurements - Investments in Certain Other Invested Assets (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Dec. 31, 2023
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	$ 4,283	$ 4,345
Private Equity Funds and Hedge Funds
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	3,550	3,799
Unfunded Commitments	959	1,081
Private equity funds
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	3,362	3,388
Unfunded Commitments	$ 959	1,081
Average original expected lives (in years)	10 years
Private equity funds | Minimum
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Extension period (in years)	1 year
Private equity funds | Maximum
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Extension period (in years)	2 years
Leveraged buyout
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	$ 1,212	1,171
Unfunded Commitments	479	558
Real assets
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	839	870
Unfunded Commitments	308	344
Venture capital
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	77	67
Unfunded Commitments	45	50
Growth equity
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	204	196
Unfunded Commitments	13	9
Mezzanine
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	129	140
Unfunded Commitments	54	56
Other
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	901	944
Unfunded Commitments	60	64
Hedge funds
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	188	411
Unfunded Commitments	0	0
Event-driven
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	13	13
Unfunded Commitments	0	0
Long-short
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	168	389
Unfunded Commitments	0	0
Macro
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	0	0
Unfunded Commitments	0	0
Other
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	7	9
Unfunded Commitments	$ 0	$ 0