Fair Value Measurements - Assets and liabilities measured at fair value on a recurring basis (Details) - USD ($)		Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Jan. 01, 2021	Dec. 31, 2020
Assets:
Bonds available for sale	[1]	$ 214,940,000,000	$ 226,156,000,000
Other bond securities, at fair value (See Note 5)	[1]	4,840,000,000	4,485,000,000
Equity securities	[1]	515,000,000	575,000,000
Derivative assets		6,499,000,000	6,049,000,000
Counterparty netting		(3,985,000,000)	(3,895,000,000)
Cash Collateral		(2,141,000,000)	(1,640,000,000)
Total derivative assets		373,000,000	514,000,000
Short-term investments	[1]	13,048,000,000	12,376,000,000
Market risk benefit assets, at fair value		978,000,000	796,000,000		$ 338,000,000	$ 338,000,000
Separate account assets		84,724,000,000	84,853,000,000
Liabilities:
Policyholder contract deposits		159,737,000,000	155,984,000,000	$ 154,852,000,000	148,223,000,000
Market risk benefit liabilities, at fair value		4,519,000,000	4,736,000,000		$ 8,739,000,000	$ 8,739,000,000
Derivative liabilities		6,716,000,000	6,043,000,000
Counterparty netting		(3,985,000,000)	(3,895,000,000)
Cash Collateral		$ (2,472,000,000)	$ (1,917,000,000)
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Other liabilities(c)	Other liabilities(c)
Total derivative liabilities		$ 259,000,000	$ 231,000,000
Fortitude Re funds withheld payable		(27,691,000,000)	(30,383,000,000)
U.S. government and government sponsored entities
Assets:
Bonds available for sale		5,954,000,000	6,619,000,000
Obligations of states, municipalities and political subdivisions
Assets:
Bonds available for sale		10,446,000,000	12,099,000,000
Non-U.S. governments
Assets:
Bonds available for sale		11,724,000,000	13,485,000,000
Corporate debt
Assets:
Bonds available for sale		126,091,000,000	137,839,000,000
RMBS
Assets:
Bonds available for sale		18,731,000,000	18,817,000,000
CMBS
Assets:
Bonds available for sale		13,510,000,000	14,193,000,000
CLO/ABS
Assets:
Bonds available for sale		28,484,000,000	23,104,000,000
Level 3
Liabilities:
Policyholder contract deposits		1,200,000,000	1,100,000,000
Level 3 | Obligations of states, municipalities and political subdivisions
Assets:
Bonds available for sale		743,000,000	799,000,000
Level 3 | Corporate debt
Assets:
Bonds available for sale		1,459,000,000	2,527,000,000
Level 3 | RMBS
Assets:
Bonds available for sale		4,855,000,000	5,235,000,000
Level 3 | CMBS
Assets:
Bonds available for sale		501,000,000	587,000,000
Fair Value Measured at Net Asset Value Per Share
Liabilities:
Fair Value Using NAV Per Share (or its equivalent)		9,600,000,000	9,800,000,000
Recurring Basis
Assets:
Counterparty netting		(3,985,000,000)	(3,895,000,000)
Cash Collateral		(2,141,000,000)	(1,640,000,000)
Counterparty netting and cash collateral		(6,126,000,000)	(5,535,000,000)
Total derivative assets		373,000,000	514,000,000
Short-term investments		6,459,000,000	5,708,000,000
Market risk benefit assets, at fair value		978,000,000	796,000,000
Liabilities:
Policyholder contract deposits		6,376,000,000	5,408,000,000
Market risk benefit liabilities, at fair value		4,519,000,000	4,736,000,000
Counterparty netting		(3,985,000,000)	(3,895,000,000)
Cash Collateral		(2,472,000,000)	(1,917,000,000)
Counterparty netting and cash collateral		(6,457,000,000)	(5,812,000,000)
Total derivative liabilities		259,000,000	231,000,000
Fortitude Re funds withheld payable		(3,413,000,000)	(2,235,000,000)
Other liabilities		351,000,000	343,000,000
Long-term debt		102,000,000	56,000,000
Recurring Basis | Levels 1, 2 and 3
Assets:
Bonds available for sale		214,940,000,000	226,156,000,000
Other bond securities, at fair value (See Note 5)		4,840,000,000	4,485,000,000
Equity securities		515,000,000	575,000,000
Other invested assets		2,376,000,000	2,220,000,000
Short-term investments		6,459,000,000	5,708,000,000
Other assets		112,000,000	107,000,000
Separate account assets		84,724,000,000	84,853,000,000
Total(d)		315,317,000,000	325,414,000,000
Liabilities:
Policyholder contract deposits		6,376,000,000	5,408,000,000
Fortitude Re funds withheld payable		(3,413,000,000)
Fortitude Re funds withheld payable			(2,235,000,000)
Other liabilities		92,000,000	112,000,000
Long-term debt		102,000,000	56,000,000
Total		7,935,000,000	8,308,000,000
Recurring Basis | Levels 1, 2 and 3 | Discontinued Operations, Excluding Held-for-Sale
Assets:
Total(d)			5,400,000,000
Recurring Basis | Levels 1, 2 and 3 | Interest rate contracts
Assets:
Derivative assets		3,248,000,000	3,722,000,000
Liabilities:
Derivative liabilities		5,174,000,000	4,838,000,000
Recurring Basis | Levels 1, 2 and 3 | Foreign exchange contracts
Assets:
Derivative assets		1,780,000,000	1,844,000,000
Liabilities:
Derivative liabilities		651,000,000	1,138,000,000
Recurring Basis | Levels 1, 2 and 3 | Equity contracts
Assets:
Derivative assets		1,422,000,000	428,000,000
Liabilities:
Derivative liabilities		853,000,000	26,000,000
Recurring Basis | Levels 1, 2 and 3 | Commodity contracts
Assets:
Derivative assets			9,000,000
Recurring Basis | Levels 1, 2 and 3 | Credit contracts
Assets:
Derivative assets		33,000,000	32,000,000
Liabilities:
Derivative liabilities		38,000,000	41,000,000
Recurring Basis | Levels 1, 2 and 3 | Other contracts
Assets:
Derivative assets		16,000,000	14,000,000
Recurring Basis | Levels 1, 2 and 3 | U.S. government and government sponsored entities
Assets:
Bonds available for sale		5,954,000,000	6,619,000,000
Recurring Basis | Levels 1, 2 and 3 | Obligations of states, municipalities and political subdivisions
Assets:
Bonds available for sale		10,446,000,000	12,099,000,000
Other bond securities, at fair value (See Note 5)		91,000,000	111,000,000
Recurring Basis | Levels 1, 2 and 3 | Non-U.S. governments
Assets:
Bonds available for sale		11,724,000,000	13,485,000,000
Other bond securities, at fair value (See Note 5)		33,000,000	66,000,000
Recurring Basis | Levels 1, 2 and 3 | Corporate debt
Assets:
Bonds available for sale		126,091,000,000	137,839,000,000
Other bond securities, at fair value (See Note 5)		2,624,000,000	2,392,000,000
Recurring Basis | Levels 1, 2 and 3 | RMBS
Assets:
Bonds available for sale		18,731,000,000	18,817,000,000
Other bond securities, at fair value (See Note 5)		267,000,000	286,000,000
Recurring Basis | Levels 1, 2 and 3 | CMBS
Assets:
Bonds available for sale		13,510,000,000	14,193,000,000
Other bond securities, at fair value (See Note 5)		278,000,000	331,000,000
Recurring Basis | Levels 1, 2 and 3 | CLO/ABS
Assets:
Bonds available for sale		28,484,000,000	23,104,000,000
Other bond securities, at fair value (See Note 5)		1,547,000,000	1,299,000,000
Recurring Basis | Level 1
Assets:
Bonds available for sale		588,000,000	183,000,000
Other bond securities, at fair value (See Note 5)		0	0
Equity securities		441,000,000	518,000,000
Other invested assets		0	0
Derivative assets		4,000,000	12,000,000
Short-term investments		2,384,000,000	2,821,000,000
Market risk benefit assets, at fair value		0	0
Other assets		0	0
Separate account assets		81,567,000,000	81,655,000,000
Total(d)		84,984,000,000	85,189,000,000
Liabilities:
Policyholder contract deposits		0	0
Market risk benefit liabilities, at fair value		0	0
Derivative liabilities		6,000,000	2,000,000
Fortitude Re funds withheld payable		0
Fortitude Re funds withheld payable			0
Other liabilities		0	0
Long-term debt		0	0
Total		6,000,000	2,000,000
Recurring Basis | Level 1 | Interest rate contracts
Assets:
Derivative assets		0	1,000,000
Liabilities:
Derivative liabilities		0	0
Recurring Basis | Level 1 | Foreign exchange contracts
Assets:
Derivative assets		0	0
Liabilities:
Derivative liabilities		0	0
Recurring Basis | Level 1 | Equity contracts
Assets:
Derivative assets		4,000,000	11,000,000
Liabilities:
Derivative liabilities		6,000,000	2,000,000
Recurring Basis | Level 1 | Commodity contracts
Assets:
Derivative assets			0
Recurring Basis | Level 1 | Credit contracts
Assets:
Derivative assets		0	0
Liabilities:
Derivative liabilities		0	0
Recurring Basis | Level 1 | Other contracts
Assets:
Derivative assets		0	0
Recurring Basis | Level 1 | U.S. government and government sponsored entities
Assets:
Bonds available for sale		338,000,000	25,000,000
Recurring Basis | Level 1 | Obligations of states, municipalities and political subdivisions
Assets:
Bonds available for sale		0	0
Other bond securities, at fair value (See Note 5)		0	0
Recurring Basis | Level 1 | Non-U.S. governments
Assets:
Bonds available for sale		250,000,000	158,000,000
Other bond securities, at fair value (See Note 5)		0	0
Recurring Basis | Level 1 | Corporate debt
Assets:
Bonds available for sale		0	0
Other bond securities, at fair value (See Note 5)		0	0
Recurring Basis | Level 1 | RMBS
Assets:
Bonds available for sale		0	0
Other bond securities, at fair value (See Note 5)		0	0
Recurring Basis | Level 1 | CMBS
Assets:
Bonds available for sale		0	0
Other bond securities, at fair value (See Note 5)		0	0
Recurring Basis | Level 1 | CLO/ABS
Assets:
Bonds available for sale		0	0
Other bond securities, at fair value (See Note 5)		0	0
Recurring Basis | Level 2
Assets:
Bonds available for sale		188,791,000,000	201,074,000,000
Other bond securities, at fair value (See Note 5)		3,387,000,000	2,958,000,000
Equity securities		15,000,000	18,000,000
Other invested assets		148,000,000	145,000,000
Derivative assets		5,537,000,000	5,395,000,000
Short-term investments		4,075,000,000	2,887,000,000
Market risk benefit assets, at fair value		0	0
Other assets		0	0
Separate account assets		3,157,000,000	3,198,000,000
Total(d)		205,110,000,000	215,675,000,000
Liabilities:
Policyholder contract deposits		49,000,000	41,000,000
Market risk benefit liabilities, at fair value		0	0
Derivative liabilities		6,670,000,000	5,995,000,000
Fortitude Re funds withheld payable		0
Fortitude Re funds withheld payable			0
Other liabilities		0	0
Long-term debt		102,000,000	56,000,000
Total		6,821,000,000	6,092,000,000
Recurring Basis | Level 2 | Interest rate contracts
Assets:
Derivative assets		2,715,000,000	3,410,000,000
Liabilities:
Derivative liabilities		5,174,000,000	4,838,000,000
Recurring Basis | Level 2 | Foreign exchange contracts
Assets:
Derivative assets		1,779,000,000	1,844,000,000
Liabilities:
Derivative liabilities		648,000,000	1,138,000,000
Recurring Basis | Level 2 | Equity contracts
Assets:
Derivative assets		1,043,000,000	132,000,000
Liabilities:
Derivative liabilities		843,000,000	10,000,000
Recurring Basis | Level 2 | Commodity contracts
Assets:
Derivative assets			9,000,000
Recurring Basis | Level 2 | Credit contracts
Assets:
Derivative assets		0	0
Liabilities:
Derivative liabilities		5,000,000	9,000,000
Recurring Basis | Level 2 | Other contracts
Assets:
Derivative assets		0	0
Recurring Basis | Level 2 | U.S. government and government sponsored entities
Assets:
Bonds available for sale		5,616,000,000	6,594,000,000
Recurring Basis | Level 2 | Obligations of states, municipalities and political subdivisions
Assets:
Bonds available for sale		9,681,000,000	11,275,000,000
Other bond securities, at fair value (See Note 5)		90,000,000	111,000,000
Recurring Basis | Level 2 | Non-U.S. governments
Assets:
Bonds available for sale		11,471,000,000	13,326,000,000
Other bond securities, at fair value (See Note 5)		33,000,000	66,000,000
Recurring Basis | Level 2 | Corporate debt
Assets:
Bonds available for sale		124,553,000,000	134,992,000,000
Other bond securities, at fair value (See Note 5)		2,403,000,000	1,976,000,000
Recurring Basis | Level 2 | RMBS
Assets:
Bonds available for sale		11,185,000,000	11,264,000,000
Other bond securities, at fair value (See Note 5)		109,000,000	113,000,000
Recurring Basis | Level 2 | CMBS
Assets:
Bonds available for sale		12,943,000,000	13,267,000,000
Other bond securities, at fair value (See Note 5)		255,000,000	303,000,000
Recurring Basis | Level 2 | CLO/ABS
Assets:
Bonds available for sale		13,342,000,000	10,356,000,000
Other bond securities, at fair value (See Note 5)		497,000,000	389,000,000
Recurring Basis | Level 3
Assets:
Bonds available for sale		25,561,000,000	24,899,000,000
Other bond securities, at fair value (See Note 5)		1,453,000,000	1,527,000,000
Equity securities		59,000,000	39,000,000
Other invested assets		2,228,000,000	2,075,000,000
Derivative assets		958,000,000	642,000,000
Short-term investments		0	0
Market risk benefit assets, at fair value		978,000,000	796,000,000	743,000,000
Other assets		112,000,000	107,000,000
Separate account assets		0	0
Total(d)		31,349,000,000	30,085,000,000
Liabilities:
Policyholder contract deposits		6,327,000,000	5,367,000,000
Market risk benefit liabilities, at fair value		4,519,000,000	4,736,000,000	$ 4,600,000,000
Derivative liabilities		40,000,000	46,000,000
Fortitude Re funds withheld payable		(3,413,000,000)
Fortitude Re funds withheld payable			(2,235,000,000)
Other liabilities		92,000,000	112,000,000
Long-term debt		0	0
Total		7,565,000,000	8,026,000,000
Recurring Basis | Level 3 | Interest rate contracts
Assets:
Derivative assets		533,000,000	311,000,000
Liabilities:
Derivative liabilities		0	0
Recurring Basis | Level 3 | Foreign exchange contracts
Assets:
Derivative assets		1,000,000	0
Liabilities:
Derivative liabilities		3,000,000	0
Recurring Basis | Level 3 | Equity contracts
Assets:
Derivative assets		375,000,000	285,000,000
Liabilities:
Derivative liabilities		4,000,000	14,000,000
Recurring Basis | Level 3 | Commodity contracts
Assets:
Derivative assets			0
Recurring Basis | Level 3 | Credit contracts
Assets:
Derivative assets		33,000,000	32,000,000
Liabilities:
Derivative liabilities		33,000,000	32,000,000
Recurring Basis | Level 3 | Other contracts
Assets:
Derivative assets		16,000,000	14,000,000
Recurring Basis | Level 3 | U.S. government and government sponsored entities
Assets:
Bonds available for sale		0	0
Recurring Basis | Level 3 | Obligations of states, municipalities and political subdivisions
Assets:
Bonds available for sale		765,000,000	824,000,000
Other bond securities, at fair value (See Note 5)		1,000,000	0
Recurring Basis | Level 3 | Non-U.S. governments
Assets:
Bonds available for sale		3,000,000	1,000,000
Other bond securities, at fair value (See Note 5)		0	0
Recurring Basis | Level 3 | Corporate debt
Assets:
Bonds available for sale		1,538,000,000	2,847,000,000
Other bond securities, at fair value (See Note 5)		221,000,000	416,000,000
Recurring Basis | Level 3 | RMBS
Assets:
Bonds available for sale		7,546,000,000	7,553,000,000
Other bond securities, at fair value (See Note 5)		158,000,000	173,000,000
Recurring Basis | Level 3 | CMBS
Assets:
Bonds available for sale		567,000,000	926,000,000
Other bond securities, at fair value (See Note 5)		23,000,000	28,000,000
Recurring Basis | Level 3 | CLO/ABS
Assets:
Bonds available for sale		15,142,000,000	12,748,000,000
Other bond securities, at fair value (See Note 5)		$ 1,050,000,000	$ 910,000,000

[1] See Note 10 for details of balances associated with variable interest entities.