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, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	$ (12)	$ 4	$ 8	$ 23
Net realized gains (losses), liabilities	$ 158	$ (60)	$ 197	$ 23
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Adjusted Revenues	Adjusted Revenues	Adjusted Revenues	Adjusted Revenues
Derivative liabilities, net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	$ 1	$ 3	$ 41	$ 18
Fortitude Re funds withheld payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	157	(57)	158	25
Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	(6)	(2)	(20)
Bonds available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	(16)	2	16	23
Other bond securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	6	(1)	7	2
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	1	0	1	2
Other invested assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	$ (3)	$ 3	$ (16)	$ (4)
Net Investment Income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net Investment Income	Net Investment Income	Net Investment Income	Net Investment Income
Net Investment Income | Derivative liabilities, net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	$ 0	$ 0	$ 0	$ 0
Net Investment Income | Fortitude Re funds withheld payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	0	0	0	0
Net Investment Income | Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities		0	0	0
Net Investment Income | Bonds available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	25	40	65	77
Net Investment Income | Other bond securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	6	(1)	7	2
Net Investment Income | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	1		1	2
Net Investment Income | Other invested assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	(3)	4	(16)	(3)
Net Realized Gains (Losses) | Derivative liabilities, net
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	1	3	41	18
Net Realized Gains (Losses) | Fortitude Re funds withheld payable
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities	157	(57)	158	25
Net Realized Gains (Losses) | Other Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), liabilities		(6)	(2)	(20)
Net Realized Gains (Losses) | Bonds available for sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	(41)	(38)	(49)	(54)
Net Realized Gains (Losses) | Other bond securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0	0	0	0
Net Realized Gains (Losses) | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	0		0	0
Net Realized Gains (Losses) | Other invested assets
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net realized gains (losses), assets	$ 0	$ (1)	$ 0	$ (1)