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Investment Information - Aging of available for sale securities in an unrealized loss position (Details) - USD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	$ 10,327	$ 12,976
Estimated Fair Value - 12 Months or More	9,687	5,671
Estimated Fair Value	20,014	18,647
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(301)	(929)
Gross Unrealized Losses - 12 Months or More	(1,031)	(720)
Gross Unrealized Losses	(1,332)	(1,649)
Fixed maturities
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	10,076	12,739
Estimated Fair Value - 12 Months or More	9,687	5,671
Estimated Fair Value	19,763	18,410
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(300)	(927)
Gross Unrealized Losses - 12 Months or More	(1,031)	(720)
Gross Unrealized Losses	(1,331)	(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	4,083	4,823
Estimated Fair Value - 12 Months or More	5,184	2,559
Estimated Fair Value	9,267	7,382
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(118)	(393)
Gross Unrealized Losses - 12 Months or More	(575)	(388)
Gross Unrealized Losses	(693)	(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	441	546
Estimated Fair Value - 12 Months or More	330	154
Estimated Fair Value	771	700
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(24)	(52)
Gross Unrealized Losses - 12 Months or More	(63)	(35)
Gross Unrealized Losses	(87)	(87)
Fixed maturities | Municipal bonds
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	126	364
Estimated Fair Value - 12 Months or More	169	16
Estimated Fair Value	295	380
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(7)	(30)
Gross Unrealized Losses - 12 Months or More	(20)	(3)
Gross Unrealized Losses	(27)	(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	127	598
Estimated Fair Value - 12 Months or More	892	445
Estimated Fair Value	1,019	1,043
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(4)	(35)
Gross Unrealized Losses - 12 Months or More	(45)	(23)
Gross Unrealized Losses	(49)	(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	3,362	3,557
Estimated Fair Value - 12 Months or More	1,085	1,443
Estimated Fair Value	4,447	5,000
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(61)	(197)
Gross Unrealized Losses - 12 Months or More	(115)	(146)
Gross Unrealized Losses	(176)	(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	1,242	1,703
Estimated Fair Value - 12 Months or More	981	542
Estimated Fair Value	2,223	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	(143)	(84)
Gross Unrealized Losses	(204)	(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	695	1,148
Estimated Fair Value - 12 Months or More	1,046	512
Estimated Fair Value	1,741	1,660
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss [Abstract]
Gross Unrealized Losses - Less than 12 Months	(25)	(66)
Gross Unrealized Losses - 12 Months or More	(70)	(41)
Gross Unrealized Losses	(95)	(107)
Short-term investments
Debt Securities, Available-for-sale, Unrealized Loss Position, Estimated Fair Value [Abstract]
Estimated Fair Value - Less than 12 Months	251	237
Estimated Fair Value - 12 Months or More	0	0
Estimated Fair Value	251	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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