Fair Value Measurements - Investments in Certain Other Invested Assets (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 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)	$ 11,195	$ 11,320
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)	9,522	9,508
Unfunded Commitments	3,701	3,748
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)	8,835	8,798
Unfunded Commitments	$ 3,701	3,748
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)	$ 3,736	3,617
Unfunded Commitments	2,278	2,313
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)	1,712	1,814
Unfunded Commitments	824	782
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)	266	270
Unfunded Commitments	136	141
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)	690	680
Unfunded Commitments	112	117
Mezzanine
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	263	292
Unfunded Commitments	94	98
Other
INVESTMENTS IN CERTAIN ENTITIES CARRIED AT FAIR VALUE USING NET ASSET VALUE PER SHARE
Fair Value Using NAV Per Share (or its equivalent)	2,168	2,125
Unfunded Commitments	257	297
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)	687	710
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)	17	18
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)	565	549
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)	37	69
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)	68	74
Unfunded Commitments	$ 0	$ 0