Fair Value Measurements - Changes in level 3 recurring fair value measurements, assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Jan. 01, 2021	Dec. 31, 2020
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	$ 29,326	$ 30,413	$ 28,647	$ 31,627
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	70	65	125	201
Other Comprehensive Income (Loss)	64	(1,180)	373	(2,665)
Purchases, Sales, Issuances and Settlements, Net	135	897	777	1,243
Gross Transfers In	136	786	518	2,197
Gross Transfers Out	(1,063)	(1,359)	(1,832)	(2,981)
Other	27	0	87	0
Fair Value End of Period	28,695	29,622	28,695	29,622
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(37)	156	(95)	105
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	5	(1,150)	$ 191	$ (2,583)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Revenues	Revenues
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Asset, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]			Other comprehensive income (loss)	Other comprehensive income (loss)
Gross Transfers Out			$ 0
Market risk benefit assets, at fair value	954		954		$ 796	$ 338	$ 338
Recurring Basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Market risk benefit assets, at fair value	954		954		796
Level 3 | Recurring Basis
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Market risk benefit assets, at fair value	954	642	$ 954	$ 642	$ 796
Net realized gains/(losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Total net realized gains (losses)	Total net realized gains (losses)
Bonds available for sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	25,722	25,404	$ 24,899	$ 26,862
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	93	85	159	230
Other Comprehensive Income (Loss)	62	(1,159)	366	(2,638)
Purchases, Sales, Issuances and Settlements, Net	(37)	707	606	792
Gross Transfers In	131	619	504	1,865
Gross Transfers Out	(1,017)	(1,288)	(1,588)	(2,743)
Other	26	0	34	0
Fair Value End of Period	24,980	24,368	24,980	24,368
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0	0	0	0
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	5	(1,150)	191	(2,583)
Bonds available for sale | Net realized gains/(losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	(28)	(57)	(24)	(76)
Bonds available for sale | Obligations of states, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	873	1,087	824	1,431
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	0	0	1	2
Other Comprehensive Income (Loss)	(3)	(143)	52	(428)
Purchases, Sales, Issuances and Settlements, Net	(1)	(4)	(8)	(65)
Gross Transfers In	0	17	0	17
Gross Transfers Out	0	0	0	0
Other	0	0	0	0
Fair Value End of Period	869	957	869	957
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0	0	0	0
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	(13)	(151)	28	(410)
Bonds available for sale | Non-U.S. governments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	9	8	1	7
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	0	0	1	0
Other Comprehensive Income (Loss)	1	0	1	0
Purchases, Sales, Issuances and Settlements, Net	(2)	0	(2)	0
Gross Transfers In	0	1	7	2
Gross Transfers Out	(2)	0	(2)	0
Other	0	0	0	0
Fair Value End of Period	6	9	6	9
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0	0	0	0
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	1	0	1	0
Bonds available for sale | Corporate debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	2,432	2,744	2,847	2,641
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	6	(15)	(96)	(26)
Other Comprehensive Income (Loss)	8	(78)	59	(151)
Purchases, Sales, Issuances and Settlements, Net	(173)	(214)	(374)	(37)
Gross Transfers In	46	252	320	382
Gross Transfers Out	(598)	(206)	(1,019)	(326)
Other	0	0	(16)	0
Fair Value End of Period	1,721	2,483	1,721	2,483
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0	0	0	0
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	5	(49)	59	(137)
Bonds available for sale | RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	7,581	8,925	7,553	10,378
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	105	92	214	222
Other Comprehensive Income (Loss)	189	(390)	119	(943)
Purchases, Sales, Issuances and Settlements, Net	(211)	(266)	(201)	(874)
Gross Transfers In	31	0	31	0
Gross Transfers Out	(43)	(9)	(64)	(431)
Other	(35)	0	(35)	0
Fair Value End of Period	7,617	8,352	7,617	8,352
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0	0	0	0
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	187	(390)	89	(925)
Bonds available for sale | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	938	864	926	1,190
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	(29)	5	(22)	13
Other Comprehensive Income (Loss)	(39)	(46)	(42)	(113)
Purchases, Sales, Issuances and Settlements, Net	(40)	85	(39)	117
Gross Transfers In	(1)	0	33	0
Gross Transfers Out	(276)	(37)	(303)	(336)
Other	0	0	0	0
Fair Value End of Period	553	871	553	871
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0	0	0	0
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	(49)	(47)	(83)	(108)
Bonds available for sale | CLO/ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	13,889	11,776	12,748	11,215
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	11	3	61	19
Other Comprehensive Income (Loss)	(94)	(502)	177	(1,003)
Purchases, Sales, Issuances and Settlements, Net	390	1,106	1,230	1,651
Gross Transfers In	55	349	113	1,464
Gross Transfers Out	(98)	(1,036)	(200)	(1,650)
Other	61	0	85	0
Fair Value End of Period	14,214	11,696	14,214	11,696
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0	0	0	0
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	(126)	(513)	97	(1,003)
Other bond securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	1,334	2,960	1,527	2,697
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	(6)	(153)	35	(274)
Other Comprehensive Income (Loss)	0	1	0	0
Purchases, Sales, Issuances and Settlements, Net	98	209	9	490
Gross Transfers In	3	167	4	285
Gross Transfers Out	(38)	(57)	(236)	(71)
Other	1	0	53	0
Fair Value End of Period	1,392	3,127	1,392	3,127
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(39)	(18)	(24)	(190)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0	0	0
Other bond securities | Net realized gains/(losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income			0	0
Other bond securities | Obligations of states, municipalities and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	1		0
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	0		0
Other Comprehensive Income (Loss)	0		0
Purchases, Sales, Issuances and Settlements, Net	2		3
Gross Transfers In	0		0
Gross Transfers Out	0		0
Other	0		0
Fair Value End of Period	3		3
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
Other bond securities | Corporate debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	130	260	416	134
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	1	(4)	2	(4)
Other Comprehensive Income (Loss)	0	0	0	0
Purchases, Sales, Issuances and Settlements, Net	24	47	(72)	124
Gross Transfers In	0	161	0	222
Gross Transfers Out	0	(3)	(191)	(15)
Other	0	0	0	0
Fair Value End of Period	155	461	155	461
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	3	(4)	2	(4)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0	0	0
Other bond securities | RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	166	199	173	196
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	2	(13)	7	(18)
Other Comprehensive Income (Loss)	0	1	0	0
Purchases, Sales, Issuances and Settlements, Net	(4)	5	(16)	14
Gross Transfers In	0	0	0	0
Gross Transfers Out	0	0	0	0
Other	0	0	0	0
Fair Value End of Period	164	192	164	192
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(3)	(13)	(5)	(21)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0	0	0
Other bond securities | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	27	33	28	35
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	(1)	(1)	(2)	(3)
Other Comprehensive Income (Loss)	0	0	0	0
Purchases, Sales, Issuances and Settlements, Net	0	0	0	0
Gross Transfers In	0	0	0	0
Gross Transfers Out	0	0	0	0
Other	0	0	0	0
Fair Value End of Period	26	32	26	32
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(1)	(1)	(2)	(3)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0	0	0
Other bond securities | CLO/ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	1,010	2,468	910	2,332
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	(8)	(135)	28	(249)
Other Comprehensive Income (Loss)	0	0	0	0
Purchases, Sales, Issuances and Settlements, Net	76	157	94	352
Gross Transfers In	3	6	4	63
Gross Transfers Out	(38)	(54)	(45)	(56)
Other	1	0	53	0
Fair Value End of Period	1,044	2,442	1,044	2,442
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(38)	0	(19)	(162)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0	0	0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	74	6	39	6
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	2	0	2	0
Other Comprehensive Income (Loss)	0	1	0	0
Purchases, Sales, Issuances and Settlements, Net	2	5	29	6
Gross Transfers In	2	0	10	0
Gross Transfers Out	(8)	0	(8)	0
Other	0	0	0	0
Fair Value End of Period	72	12	72	12
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	2	0	2	0
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0	0	0
Other invested assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	2,086	1,935	2,075	1,948
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	(19)	133	(71)	245
Other Comprehensive Income (Loss)	2	(23)	7	(27)
Purchases, Sales, Issuances and Settlements, Net	71	(23)	129	(38)
Gross Transfers In	0	0	0	47
Gross Transfers Out	0	(14)	0	(167)
Other	0	0	0	0
Fair Value End of Period	2,140	2,008	2,140	2,008
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0	174	(73)	295
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0	0	0
Other invested assets | Net realized gains/(losses)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	1		0	0
Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	110	108	107	114
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	0	0	0	0
Other Comprehensive Income (Loss)	0	0	0	0
Purchases, Sales, Issuances and Settlements, Net	1	(1)	4	(7)
Gross Transfers In	0	0	0	0
Gross Transfers Out	0	0	0	0
Other	0	0	0	0
Fair Value End of Period	111	107	111	107
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0	0	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	$ 0	$ 0