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Investment Information - Aging of available for sale securities in an unrealized loss position (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	$ 6,934	$ 12,976
Estimated Fair Value - 12 Months or More	10,006	5,671
Estimated Fair Value	16,940	18,647
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(266)	(929)
Gross Unrealized Losses - 12 Months or More	(1,032)	(720)
Gross Unrealized Losses	(1,298)	(1,649)
Fixed maturities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	6,660	12,739
Estimated Fair Value - 12 Months or More	10,006	5,671
Estimated Fair Value	16,666	18,410
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(265)	(927)
Gross Unrealized Losses - 12 Months or More	(1,032)	(720)
Gross Unrealized Losses	(1,297)	(1,647)
Fixed maturities | Corporate bonds
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	2,723	4,823
Estimated Fair Value - 12 Months or More	4,702	2,559
Estimated Fair Value	7,425	7,382
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(101)	(393)
Gross Unrealized Losses - 12 Months or More	(535)	(388)
Gross Unrealized Losses	(636)	(781)
Fixed maturities | Residential mortgage backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	412	546
Estimated Fair Value - 12 Months or More	279	154
Estimated Fair Value	691	700
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(18)	(52)
Gross Unrealized Losses - 12 Months or More	(56)	(35)
Gross Unrealized Losses	(74)	(87)
Fixed maturities | Municipal bonds
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	131	364
Estimated Fair Value - 12 Months or More	164	16
Estimated Fair Value	295	380
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(6)	(30)
Gross Unrealized Losses - 12 Months or More	(18)	(3)
Gross Unrealized Losses	(24)	(33)
Fixed maturities | Commercial mortgage backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	167	598
Estimated Fair Value - 12 Months or More	855	445
Estimated Fair Value	1,022	1,043
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(8)	(35)
Gross Unrealized Losses - 12 Months or More	(46)	(23)
Gross Unrealized Losses	(54)	(58)
Fixed maturities | 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	1,209	3,557
Estimated Fair Value - 12 Months or More	2,137	1,443
Estimated Fair Value	3,346	5,000
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(40)	(197)
Gross Unrealized Losses - 12 Months or More	(194)	(146)
Gross Unrealized Losses	(234)	(343)
Fixed maturities | Non-U.S. government securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	1,109	1,703
Estimated Fair Value - 12 Months or More	863	542
Estimated Fair Value	1,972	2,245
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(61)	(154)
Gross Unrealized Losses - 12 Months or More	(117)	(84)
Gross Unrealized Losses	(178)	(238)
Fixed maturities | Asset backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	909	1,148
Estimated Fair Value - 12 Months or More	1,006	512
Estimated Fair Value	1,915	1,660
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(31)	(66)
Gross Unrealized Losses - 12 Months or More	(66)	(41)
Gross Unrealized Losses	(97)	(107)
Short-term investments
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	274	237
Estimated Fair Value - 12 Months or More	0	0
Estimated Fair Value	274	237
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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