Fair Value Measurements - Net realized and unrealized gains and losses included in income related to level 3 assets and liabilities (Details) - USD ($)
$ in Millions

Fair Value Measurements - Net realized and unrealized gains and losses included in income related to level 3 assets and liabilities (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	$ 4	$ (18)	$ (8)	$ 391
Net realized gains (losses), liabilities	1,595	(1,473)	(37)	(3,456)
Policyholder contract deposits
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	788	(948)	(372)	(1,841)
Policyholder contract deposits \| Income Statement Location [Axis]: us-gaap:InsuranceCommissionsAndFees
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Policyholder contract deposits \| Income Statement Location [Axis]: us-gaap:MarketRiskBenefitChangeInFairValueGainLoss
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Policyholder contract deposits \| Income Statement Location [Axis]: us-gaap:NetInvestmentIncome
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Policyholder contract deposits \| Income Statement Location [Axis]: us-gaap:RealizedInvestmentGainsLosses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	788	(948)	(372)	(1,841)
Derivative liabilities, net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	(225)	145	(395)	(98)
Derivative liabilities, net \| Income Statement Location [Axis]: us-gaap:InsuranceCommissionsAndFees
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	16	15	49	47
Derivative liabilities, net \| Income Statement Location [Axis]: us-gaap:MarketRiskBenefitChangeInFairValueGainLoss
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Derivative liabilities, net \| Income Statement Location [Axis]: us-gaap:NetInvestmentIncome
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Derivative liabilities, net \| Income Statement Location [Axis]: us-gaap:RealizedInvestmentGainsLosses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	(241)	130	(444)	(145)
Fortitude Re funds withheld payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	1,032	(670)	730	(1,517)
Fortitude Re funds withheld payable \| Income Statement Location [Axis]: us-gaap:InsuranceCommissionsAndFees
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Fortitude Re funds withheld payable \| Income Statement Location [Axis]: us-gaap:MarketRiskBenefitChangeInFairValueGainLoss
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Fortitude Re funds withheld payable \| Income Statement Location [Axis]: us-gaap:NetInvestmentIncome
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Fortitude Re funds withheld payable \| Income Statement Location [Axis]: us-gaap:RealizedInvestmentGainsLosses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	1,032	(670)	730	(1,517)
Market risk benefit liabilities, net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	15	(57)	(527)	(105)
Market risk benefit liabilities, net \| Income Statement Location [Axis]: us-gaap:InsuranceCommissionsAndFees
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Market risk benefit liabilities, net \| Income Statement Location [Axis]: us-gaap:MarketRiskBenefitChangeInFairValueGainLoss
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	16	(58)	(527)	(103)
Market risk benefit liabilities, net \| Income Statement Location [Axis]: us-gaap:NetInvestmentIncome
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Market risk benefit liabilities, net \| Income Statement Location [Axis]: us-gaap:RealizedInvestmentGainsLosses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	(1)	1	0	(2)
Bonds available-for-sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	36	(22)	70	350
Bonds available-for-sale \| Income Statement Location [Axis]: us-gaap:InsuranceCommissionsAndFees
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Bonds available-for-sale \| Income Statement Location [Axis]: us-gaap:MarketRiskBenefitChangeInFairValueGainLoss
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Bonds available-for-sale \| Income Statement Location [Axis]: us-gaap:NetInvestmentIncome
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	19	35	75	332
Bonds available-for-sale \| Income Statement Location [Axis]: us-gaap:RealizedInvestmentGainsLosses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	17	(57)	(5)	18
Other bond securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	(37)	13	(63)	41
Other bond securities \| Income Statement Location [Axis]: us-gaap:InsuranceCommissionsAndFees
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Other bond securities \| Income Statement Location [Axis]: us-gaap:MarketRiskBenefitChangeInFairValueGainLoss
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Other bond securities \| Income Statement Location [Axis]: us-gaap:NetInvestmentIncome
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	(37)	13	(63)	41
Other bond securities \| Income Statement Location [Axis]: us-gaap:RealizedInvestmentGainsLosses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	11	(21)	11
Equity securities \| Income Statement Location [Axis]: us-gaap:InsuranceCommissionsAndFees
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Equity securities \| Income Statement Location [Axis]: us-gaap:MarketRiskBenefitChangeInFairValueGainLoss
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Equity securities \| Income Statement Location [Axis]: us-gaap:NetInvestmentIncome
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	11	(21)	11
Equity securities \| Income Statement Location [Axis]: us-gaap:RealizedInvestmentGainsLosses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Other invested assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	5	(20)	6	(11)
Other invested assets \| Income Statement Location [Axis]: us-gaap:InsuranceCommissionsAndFees
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Other invested assets \| Income Statement Location [Axis]: us-gaap:MarketRiskBenefitChangeInFairValueGainLoss
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Other invested assets \| Income Statement Location [Axis]: us-gaap:NetInvestmentIncome
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	3	(20)	2	1
Other invested assets \| Income Statement Location [Axis]: us-gaap:RealizedInvestmentGainsLosses
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	$ 2	$ 0	$ 4	$ (12)