Fair Value Measurements - Changes in Level 3 Recurring Fair Value Measurements, Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Derivative liabilities, net
Fair Value Beginning of Year	$ (19)	$ (28)	$ (479)
Net Realized and Unrealized (Gains) Losses Included in Income	139	114
Other Comprehensive (Income) Loss	0	0
Purchases, Sales, Issuances and Settlements, Net	(130)	302
Gross Transfers In	0	0
Gross Transfers Out	0	0
Other	0	35
Fair Value End of Period	(19)	(28)
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(93)	(27)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	$ 0	$ 0
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Revenues	Revenues
Fair Value, Liability, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]	Other comprehensive income	Other comprehensive income
Fair Value, Liability, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Realized Investment Gains (Losses)	Realized Investment Gains (Losses)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 3,898	$ 3,481	4,151
Net Realized and Unrealized Gains (Losses) Included in Income	18	6
Other Comprehensive Income (Loss)	27	96
Purchases, Sales, Issuances and Settlements, Net	759	(926)
Gross Transfers In	184	705
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	(568)	(601)
Other	(3)	50
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	11	(9)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	44	(16)
Equity securities
Derivative liabilities, net
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	55	15	14
Net Realized and Unrealized Gains (Losses) Included in Income	4	1
Other Comprehensive Income (Loss)	0	0
Purchases, Sales, Issuances and Settlements, Net	18	4
Gross Transfers In	18	11
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	0	(13)
Other	0	(2)
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	1	1
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0
Other invested assets
Derivative liabilities, net
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	92	163	221
Net Realized and Unrealized Gains (Losses) Included in Income	(3)	(16)
Other Comprehensive Income (Loss)	0	0
Purchases, Sales, Issuances and Settlements, Net	(25)	(35)
Gross Transfers In	1	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3	(63)	(13)
Other	19	6
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	1	(11)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0
Derivative liabilities, net
Derivative liabilities, net
Fair Value Beginning of Period	0	(453)
Net Realized and Unrealized (Gains) Losses Included in Income		41
Other Comprehensive (Income) Loss		0
Purchases, Sales, Issuances and Settlements, Net		377
Gross Transfers In		0
Gross Transfers Out		0
Other		35
Fair Value End of Year		0
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period		(1)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period		0
Net Realized and Unrealized (Gains) Losses Included in Income		41
Fortitude Re funds withheld payable
Derivative liabilities, net
Fair Value Beginning of Year	(92)	(128)	(148)
Net Realized and Unrealized (Gains) Losses Included in Income	166	75
Other Comprehensive (Income) Loss	0	0
Purchases, Sales, Issuances and Settlements, Net	(130)	(55)
Gross Transfers In	0	0
Gross Transfers Out	0	0
Other	0	0
Fair Value End of Period	(92)	(128)
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(93)	(26)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0
Other Liabilities
Derivative liabilities, net
Fair Value Beginning of Year	73	100	$ 122
Net Realized and Unrealized (Gains) Losses Included in Income	(27)	(2)
Other Comprehensive (Income) Loss	0	0
Purchases, Sales, Issuances and Settlements, Net	0	(20)
Gross Transfers In	0	0
Gross Transfers Out	0	0
Other	0	0
Fair Value End of Period	73	100
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0	0
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	$ 0	$ 0