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	Jun. 30, 2026	Dec. 31, 2025
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	$ 45,264	$ 45,762
U.S. government, agencies and government-sponsored enterprises
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	3,624	3,701
State and political subdivisions
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,999	2,114
Non-U.S. government
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,333	1,215
U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	26,355	27,046
Non-U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	7,018	7,191
Residential mortgage-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,069	1,100
Commercial mortgage-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,361	1,309
Other asset-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	2,505	2,086
Level 2
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	42,021	42,691
Level 2 \| U.S. government, agencies and government-sponsored enterprises
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	3,624	3,701
Level 2 \| State and political subdivisions
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,999	2,114
Level 2 \| Non-U.S. government
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,318	1,199
Level 2 \| U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	24,360	25,089
Level 2 \| Non-U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	6,269	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	1,341	1,290
Level 2 \| Other asset-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	2,048	$ 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	3,624
Level 2 \| Third-Party Pricing Services \| Fixed maturity securities: \| State and political subdivisions
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,999
Level 2 \| Third-Party Pricing Services \| Fixed maturity securities: \| Non-U.S. government
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	1,318
Level 2 \| Third-Party Pricing Services \| Fixed maturity securities: \| U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	22,620
Level 2 \| Third-Party Pricing Services \| Fixed maturity securities: \| Non-U.S. corporate
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	5,508
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	1,341
Level 2 \| Third-Party Pricing Services \| Fixed maturity securities: \| Other asset-backed
Fair value measurements Significant unobservable inputs [Line Items]
Fixed maturity securities	$ 2,048

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