Fair Value of Financial Instruments - Schedule of Significant Inputs Used by Third-Party Pricing Services for Certain Fair Value Measurements of Fixed Maturity Securities that Classified as Level 2 (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	$ 45,095	$ 45,762
U.S. government, agencies and government-sponsored enterprises
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	3,616	3,701
State and political subdivisions
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	2,086	2,114
Non-U.S. government
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,191	1,215
U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	26,509	27,046
Non-U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	7,045	7,191
Residential mortgage-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,064	1,100
Commercial mortgage-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,358	1,309
Other asset-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	2,226	2,086
Level 2
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	42,072	42,691
Level 2 | U.S. government, agencies and government-sponsored enterprises
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	3,616	3,701
Level 2 | State and political subdivisions
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	2,086	2,114
Level 2 | Non-U.S. government
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,176	1,199
Level 2 | U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	24,621	25,089
Level 2 | Non-U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	6,308	6,442
Level 2 | Residential mortgage-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,062	1,097
Level 2 | Commercial mortgage-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,338	1,290
Level 2 | Other asset-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,865	$ 1,759
Level 2 | Third-Party Pricing Services | Fixed maturity securities: | U.S. government, agencies and government-sponsored enterprises
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	3,616
Level 2 | Third-Party Pricing Services | Fixed maturity securities: | State and political subdivisions
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	2,086
Level 2 | Third-Party Pricing Services | Fixed maturity securities: | Non-U.S. government
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,176
Level 2 | Third-Party Pricing Services | Fixed maturity securities: | U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	22,854
Level 2 | Third-Party Pricing Services | Fixed maturity securities: | Non-U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	5,530
Level 2 | Third-Party Pricing Services | Fixed maturity securities: | Residential mortgage-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,062
Level 2 | Third-Party Pricing Services | Fixed maturity securities: | Commercial mortgage-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,338
Level 2 | Third-Party Pricing Services | Fixed maturity securities: | Other asset-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	$ 1,865