Investment Information - Aging of available for sale securities in an unrealized loss position (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	$ 6,143	$ 12,494
Estimated Fair Value - 12 Months or More	3,604	5,080
Estimated Fair Value	9,747	17,574
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(147)	(290)
Gross Unrealized Losses - 12 Months or More	(248)	(404)
Gross Unrealized Losses	(395)	(694)
Fixed maturities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	5,749	12,397
Estimated Fair Value - 12 Months or More	3,604	5,080
Estimated Fair Value	9,353	17,477
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(146)	(288)
Gross Unrealized Losses - 12 Months or More	(248)	(404)
Gross Unrealized Losses	(394)	(692)
Corporate bonds
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	1,944	4,582
Estimated Fair Value - 12 Months or More	2,043	2,924
Estimated Fair Value	3,987	7,506
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(83)	(114)
Gross Unrealized Losses - 12 Months or More	(135)	(232)
Gross Unrealized Losses	(218)	(346)
U.S. government and government agencies
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	1,727	5,130
Estimated Fair Value - 12 Months or More	308	516
Estimated Fair Value	2,035	5,646
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(29)	(100)
Gross Unrealized Losses - 12 Months or More	(19)	(49)
Gross Unrealized Losses	(48)	(149)
Non-U.S. government securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	1,132	1,650
Estimated Fair Value - 12 Months or More	395	418
Estimated Fair Value	1,527	2,068
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(25)	(58)
Gross Unrealized Losses - 12 Months or More	(45)	(49)
Gross Unrealized Losses	(70)	(107)
Residential mortgage backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	158	571
Estimated Fair Value - 12 Months or More	175	186
Estimated Fair Value	333	757
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(3)	(6)
Gross Unrealized Losses - 12 Months or More	(21)	(25)
Gross Unrealized Losses	(24)	(31)
Asset backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	497	236
Estimated Fair Value - 12 Months or More	348	426
Estimated Fair Value	845	662
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(4)	(8)
Gross Unrealized Losses - 12 Months or More	(16)	(24)
Gross Unrealized Losses	(20)	(32)
Commercial mortgage backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	276	180
Estimated Fair Value - 12 Months or More	188	434
Estimated Fair Value	464	614
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(2)	(1)
Gross Unrealized Losses - 12 Months or More	(5)	(10)
Gross Unrealized Losses	(7)	(11)
Municipal bonds
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	15	48
Estimated Fair Value - 12 Months or More	147	176
Estimated Fair Value	162	224
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	0	(1)
Gross Unrealized Losses - 12 Months or More	(7)	(15)
Gross Unrealized Losses	(7)	(16)
Short-term investments
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	394	97
Estimated Fair Value - 12 Months or More	0	0
Estimated Fair Value	394	97
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(1)	(2)
Gross Unrealized Losses - 12 Months or More	0	0
Gross Unrealized Losses	$ (1)	$ (2)

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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