Investments - Value of Other Securities Measured at Fair Value Based on Election of the Fair Value Option (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2026	Dec. 31, 2025
Debt and Equity Securities, FV-NI [Line Items]
Other bond securities	$ 677	$ 741
Equity securities	1,616	502
Onex Corporation
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	548
Corebridge Financial Inc
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	607
Fixed Maturities And Equity Securities
Debt and Equity Securities, FV-NI [Line Items]
Total	$ 2,293	$ 1,243
Fixed Maturities And Equity Securities \| Investment Concentration Risk \| Investments
Debt and Equity Securities, FV-NI [Line Items]
Concentration risk (as a percent)	100.00%	100.00%
Fixed maturity securities
Debt and Equity Securities, FV-NI [Line Items]
Other bond securities	$ 677	$ 741
Fixed maturity securities \| Investment Concentration Risk \| Investments
Debt and Equity Securities, FV-NI [Line Items]
Concentration risk (as a percent)	30.00%	59.00%
Fixed maturity securities \| Obligations of states, municipalities and political subdivisions
Debt and Equity Securities, FV-NI [Line Items]
Other bond securities	$ 50	$ 51
Fixed maturity securities \| Obligations of states, municipalities and political subdivisions \| Investment Concentration Risk \| Investments
Debt and Equity Securities, FV-NI [Line Items]
Concentration risk (as a percent)	2.00%	4.00%
Fixed maturity securities \| Non-U.S. governments
Debt and Equity Securities, FV-NI [Line Items]
Other bond securities	$ 21	$ 23
Fixed maturity securities \| Non-U.S. governments \| Investment Concentration Risk \| Investments
Debt and Equity Securities, FV-NI [Line Items]
Concentration risk (as a percent)	1.00%	2.00%
Fixed maturity securities \| Corporate debt
Debt and Equity Securities, FV-NI [Line Items]
Other bond securities	$ 204	$ 274
Fixed maturity securities \| Corporate debt \| Investment Concentration Risk \| Investments
Debt and Equity Securities, FV-NI [Line Items]
Concentration risk (as a percent)	9.00%	22.00%
Fixed maturity securities \| Mortgage-backed, asset-backed and collateralized
Debt and Equity Securities, FV-NI [Line Items]
Other bond securities	$ 402	$ 393
Fixed maturity securities \| Mortgage-backed, asset-backed and collateralized \| Investment Concentration Risk \| Investments
Debt and Equity Securities, FV-NI [Line Items]
Concentration risk (as a percent)	18.00%	31.00%
Fixed maturity securities \| RMBS
Debt and Equity Securities, FV-NI [Line Items]
Other bond securities	$ 93	$ 97
Fixed maturity securities \| RMBS \| Investment Concentration Risk \| Investments
Debt and Equity Securities, FV-NI [Line Items]
Concentration risk (as a percent)	4.00%	8.00%
Fixed maturity securities \| CMBS
Debt and Equity Securities, FV-NI [Line Items]
Other bond securities	$ 42	$ 42
Fixed maturity securities \| CMBS \| Investment Concentration Risk \| Investments
Debt and Equity Securities, FV-NI [Line Items]
Concentration risk (as a percent)	2.00%	3.00%
Fixed maturity securities \| CLO/ABS
Debt and Equity Securities, FV-NI [Line Items]
Other bond securities	$ 267	$ 254
Fixed maturity securities \| CLO/ABS \| Investment Concentration Risk \| Investments
Debt and Equity Securities, FV-NI [Line Items]
Concentration risk (as a percent)	12.00%	20.00%
Equity securities
Debt and Equity Securities, FV-NI [Line Items]
Equity securities	$ 1,616	$ 502
Equity securities \| Investment Concentration Risk \| Investments
Debt and Equity Securities, FV-NI [Line Items]
Concentration risk (as a percent)	70.00%	41.00%

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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