Fair Value Measurements - Changes in level 3 recurring fair value measurements, assets (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 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	$ 28,647	$ 31,627
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	55	136
Other Comprehensive Income (Loss)	309	(1,485)
Purchases, Sales, Issuances and Settlements, Net	642	346
Gross Transfers In	382	1,411
Gross Transfers Out	(769)	(1,622)
Other	60	0
Fair Value End of Period	29,326	30,413
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(27)	(50)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	$ 191	$ (1,451)
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	830		$ 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	830		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	$ 830	$ 666	$ 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	$ 24,899	$ 26,862
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	66	145
Other Comprehensive Income (Loss)	304	(1,479)
Purchases, Sales, Issuances and Settlements, Net	643	85
Gross Transfers In	373	1,246
Gross Transfers Out	(571)	(1,455)
Other	8	0
Fair Value End of Period	25,722	25,404
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	191	(1,451)
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	4	(19)
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	824	1,431
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	1	2
Other Comprehensive Income (Loss)	55	(285)
Purchases, Sales, Issuances and Settlements, Net	(7)	(61)
Gross Transfers In	0	0
Gross Transfers Out	0	0
Other	0	0
Fair Value End of Period	873	1,087
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	44	(273)
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	1	7
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	1	0
Other Comprehensive Income (Loss)	0	0
Purchases, Sales, Issuances and Settlements, Net	0	0
Gross Transfers In	7	1
Gross Transfers Out	0	0
Other	0	0
Fair Value End of Period	9	8
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
Bonds available for sale | Corporate debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	2,847	2,641
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	(102)	(11)
Other Comprehensive Income (Loss)	51	(73)
Purchases, Sales, Issuances and Settlements, Net	(201)	177
Gross Transfers In	274	130
Gross Transfers Out	(421)	(120)
Other	(16)	0
Fair Value End of Period	2,432	2,744
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	50	(69)
Bonds available for sale | RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	7,553	10,378
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	109	130
Other Comprehensive Income (Loss)	(70)	(553)
Purchases, Sales, Issuances and Settlements, Net	10	(608)
Gross Transfers In	0	0
Gross Transfers Out	(21)	(422)
Other	0	0
Fair Value End of Period	7,581	8,925
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	(98)	(544)
Bonds available for sale | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	926	1,190
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	7	8
Other Comprehensive Income (Loss)	(3)	(67)
Purchases, Sales, Issuances and Settlements, Net	1	32
Gross Transfers In	34	0
Gross Transfers Out	(27)	(299)
Other	0	0
Fair Value End of Period	938	864
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	(34)	(64)
Bonds available for sale | CLO/ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	12,748	11,215
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	50	16
Other Comprehensive Income (Loss)	271	(501)
Purchases, Sales, Issuances and Settlements, Net	840	545
Gross Transfers In	58	1,115
Gross Transfers Out	(102)	(614)
Other	24	0
Fair Value End of Period	13,889	11,776
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	229	(501)
Other bond securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	1,527	2,697
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	41	(121)
Other Comprehensive Income (Loss)	0	(1)
Purchases, Sales, Issuances and Settlements, Net	(89)	281
Gross Transfers In	1	118
Gross Transfers Out	(198)	(14)
Other	52	0
Fair Value End of Period	1,334	2,960
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	23	(171)
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 | 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	0
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	0
Other Comprehensive Income (Loss)	0
Purchases, Sales, Issuances and Settlements, Net	1
Gross Transfers In	0
Gross Transfers Out	0
Other	0
Fair Value End of Period	1
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	0
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0
Other bond securities | Corporate debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	416	134
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	1	0
Other Comprehensive Income (Loss)	0	0
Purchases, Sales, Issuances and Settlements, Net	(96)	77
Gross Transfers In	0	61
Gross Transfers Out	(191)	(12)
Other	0	0
Fair Value End of Period	130	260
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	3	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 | RMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	173	196
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	5	(5)
Other Comprehensive Income (Loss)	0	(1)
Purchases, Sales, Issuances and Settlements, Net	(12)	9
Gross Transfers In	0	0
Gross Transfers Out	0	0
Other	0	0
Fair Value End of Period	166	199
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(3)	(8)
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 | CMBS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	28	35
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	(1)	(2)
Other Comprehensive Income (Loss)	0	0
Purchases, Sales, Issuances and Settlements, Net	0	0
Gross Transfers In	0	0
Gross Transfers Out	0	0
Other	0	0
Fair Value End of Period	27	33
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(1)	(2)
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 | CLO/ABS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	910	2,332
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	36	(114)
Other Comprehensive Income (Loss)	0	0
Purchases, Sales, Issuances and Settlements, Net	18	195
Gross Transfers In	1	57
Gross Transfers Out	(7)	(2)
Other	52	0
Fair Value End of Period	1,010	2,468
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	24	(161)
Changes in Unrealized Gains (Losses) Included in Other Comprehensive Income (Loss) for Recurring Level 3 Instruments Held at End of Period	0	0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	39	6
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	0	0
Other Comprehensive Income (Loss)	0	(1)
Purchases, Sales, Issuances and Settlements, Net	27	1
Gross Transfers In	8	0
Gross Transfers Out	0	0
Other	0	0
Fair Value End of Period	74	6
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 invested assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	2,075	1,948
MRBs and Net Realized and Unrealized Gains (Losses) Included in Income	(52)	112
Other Comprehensive Income (Loss)	5	(4)
Purchases, Sales, Issuances and Settlements, Net	58	(15)
Gross Transfers In	0	47
Gross Transfers Out	0	(153)
Other	0	0
Fair Value End of Period	2,086	1,935
Changes in Unrealized Gains (Losses) Included in Income on Instruments Held at End of Period	(50)	121
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 | 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
Other assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair Value Beginning of Period	107	114
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	3	(6)
Gross Transfers In	0	0
Gross Transfers Out	0	0
Other	0	0
Fair Value End of Period	110	108
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