Fair Value Measurements - Assets and liabilities measured at fair value on a recurring basis (Details) - USD ($)		Dec. 31, 2023	Dec. 31, 2022	Jan. 01, 2021	Dec. 31, 2020
Assets:
Bonds available for sale	[1]	$ 231,733,000,000	$ 226,156,000,000
Other bond securities, at fair value (See Note 5)	[1]	5,241,000,000	4,485,000,000
Equity securities	[1]	728,000,000	575,000,000
Derivative assets		6,595,000,000	6,049,000,000
Counterparty netting		(3,864,000,000)	(3,895,000,000)
Cash Collateral		$ (2,220,000,000)	$ (1,640,000,000)
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other assets	Other assets
Total derivative assets		$ 511,000,000	$ 514,000,000
Short-term investments	[1]	17,200,000,000	12,376,000,000
Market risk benefit assets, at fair value		912,000,000	796,000,000	$ 338,000,000	$ 338,000,000
Separate account assets		91,005,000,000	84,853,000,000
Liabilities:
Policyholder contract deposits		161,979,000,000	155,984,000,000	148,223,000,000
Market risk benefit liabilities, at fair value		5,705,000,000	4,736,000,000	$ 8,739,000,000	$ 8,739,000,000
Derivative liabilities		5,309,000,000	6,043,000,000
Counterparty netting		(3,864,000,000)	(3,895,000,000)
Cash Collateral		$ (1,050,000,000)	$ (1,917,000,000)
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Other liabilities(c)	Other liabilities(c)
Total derivative liabilities		$ 395,000,000	$ 231,000,000
Fortitude Re funds withheld payable		(29,484,000,000)	(30,383,000,000)
Fair Value Using NAV Per Share (or its equivalent)		11,320,000,000	11,809,000,000
Short-term and long-term debt		22,387,000,000	27,179,000,000
Estimated Fair Value
Assets:
Short-term investments		6,428,000,000	6,668,000,000
Liabilities:
Fortitude Re funds withheld payable		(30,710,000,000)	(32,618,000,000)
Carrying Value
Assets:
Short-term investments		6,428,000,000	6,668,000,000
Liabilities:
Fortitude Re funds withheld payable		(30,710,000,000)	(32,618,000,000)
Consolidated Entities, Excluding Consolidated Investments
Liabilities:
Short-term and long-term debt		19,796,000,000	21,299,000,000
Consolidated Entities, Excluding Consolidated Investments | Estimated Fair Value
Liabilities:
Short-term and long-term debt		18,862,000,000	19,603,000,000
Consolidated Entities, Excluding Consolidated Investments | Carrying Value
Liabilities:
Short-term and long-term debt		19,743,000,000	21,243,000,000
Consolidated Investments, Including Variable Interest Entities, Primarily Beneficiary
Liabilities:
Short-term and long-term debt	[1]	2,591,000,000	5,880,000,000
Consolidated Investments, Including Variable Interest Entities, Primarily Beneficiary | Estimated Fair Value
Liabilities:
Debt		2,569,000,000	5,533,000,000
Consolidated Investments, Including Variable Interest Entities, Primarily Beneficiary | Carrying Value
Liabilities:
Debt		2,591,000,000	5,880,000,000
U.S. government and government sponsored entities
Assets:
Bonds available for sale		5,616,000,000	6,619,000,000
Obligations of states, municipalities and political subdivisions
Assets:
Bonds available for sale		10,663,000,000	12,099,000,000
Non-U.S. governments
Assets:
Bonds available for sale		12,453,000,000	13,485,000,000
Corporate debt
Assets:
Bonds available for sale		138,432,000,000	137,839,000,000
RMBS
Assets:
Bonds available for sale		20,444,000,000	18,817,000,000
CMBS
Assets:
Bonds available for sale		14,128,000,000	14,193,000,000
CLO/ABS
Assets:
Bonds available for sale		29,997,000,000	23,104,000,000
Level 1 | Estimated Fair Value
Assets:
Short-term investments		0	0
Liabilities:
Fortitude Re funds withheld payable		0	0
Level 1 | Consolidated Entities, Excluding Consolidated Investments | Estimated Fair Value
Liabilities:
Short-term and long-term debt		0	0
Level 1 | Consolidated Investments, Including Variable Interest Entities, Primarily Beneficiary | Estimated Fair Value
Liabilities:
Debt		0	0
Level 2 | Estimated Fair Value
Assets:
Short-term investments		6,428,000,000	6,668,000,000
Liabilities:
Fortitude Re funds withheld payable		0	0
Level 2 | Consolidated Entities, Excluding Consolidated Investments | Estimated Fair Value
Liabilities:
Short-term and long-term debt		18,595,000,000	19,328,000,000
Level 2 | Consolidated Investments, Including Variable Interest Entities, Primarily Beneficiary | Estimated Fair Value
Liabilities:
Debt		43,000,000	3,055,000,000
Level 3
Liabilities:
Policyholder contract deposits		1,500,000,000	1,100,000,000
Level 3 | Estimated Fair Value
Assets:
Short-term investments		0	0
Liabilities:
Fortitude Re funds withheld payable		(30,710,000,000)	(32,618,000,000)
Level 3 | Consolidated Entities, Excluding Consolidated Investments | Estimated Fair Value
Liabilities:
Short-term and long-term debt		267,000,000	275,000,000
Level 3 | Consolidated Investments, Including Variable Interest Entities, Primarily Beneficiary | Estimated Fair Value
Liabilities:
Debt		2,526,000,000	2,478,000,000
Level 3 | Obligations of states, municipalities and political subdivisions
Assets:
Bonds available for sale		824,000,000	799,000,000
Level 3 | Corporate debt
Assets:
Bonds available for sale		1,803,000,000	2,527,000,000
Level 3 | RMBS
Assets:
Bonds available for sale		4,656,000,000	5,235,000,000
Level 3 | CMBS
Assets:
Bonds available for sale		587,000,000	587,000,000
Fair Value Measured at Net Asset Value Per Share
Liabilities:
Fair Value Using NAV Per Share (or its equivalent)		9,500,000,000	9,800,000,000
Recurring Basis
Assets:
Counterparty netting		(3,864,000,000)	(3,895,000,000)
Cash Collateral		(2,220,000,000)	(1,640,000,000)
Counterparty netting and cash collateral		(6,084,000,000)	(5,535,000,000)
Total derivative assets		511,000,000	514,000,000
Short-term investments		10,772,000,000	5,708,000,000
Market risk benefit assets, at fair value		912,000,000	796,000,000
Liabilities:
Policyholder contract deposits		7,997,000,000	5,408,000,000
Market risk benefit liabilities, at fair value		5,705,000,000	4,736,000,000
Counterparty netting		(3,864,000,000)	(3,895,000,000)
Cash Collateral		(1,050,000,000)	(1,917,000,000)
Counterparty netting and cash collateral		(4,914,000,000)	(5,812,000,000)
Total derivative liabilities		395,000,000	231,000,000
Fortitude Re funds withheld payable		(1,226,000,000)	(2,235,000,000)
Other liabilities		624,000,000	343,000,000
Long-term debt		53,000,000	56,000,000
Recurring Basis | Levels 1, 2 and 3
Assets:
Bonds available for sale		231,733,000,000	226,156,000,000
Other bond securities, at fair value (See Note 5)		5,241,000,000	4,485,000,000
Equity securities		728,000,000	575,000,000
Other invested assets		2,225,000,000	2,220,000,000
Short-term investments		10,772,000,000	5,708,000,000
Other assets		243,000,000	107,000,000
Separate account assets		91,005,000,000	84,853,000,000
Total(d)		343,370,000,000	325,414,000,000
Liabilities:
Policyholder contract deposits		7,997,000,000	5,408,000,000
Fortitude Re funds withheld payable		(1,226,000,000)
Fortitude Re funds withheld payable			(2,235,000,000)
Other liabilities		229,000,000	112,000,000
Long-term debt		53,000,000	56,000,000
Total		13,153,000,000	8,308,000,000
Recurring Basis | Levels 1, 2 and 3 | Discontinued Operations, Excluding Held-for-Sale
Assets:
Total(d)			182,000,000
Recurring Basis | Levels 1, 2 and 3 | Interest rate contracts
Assets:
Derivative assets		3,286,000,000	3,722,000,000
Liabilities:
Derivative liabilities		3,631,000,000	4,838,000,000
Recurring Basis | Levels 1, 2 and 3 | Foreign exchange contracts
Assets:
Derivative assets		1,236,000,000	1,844,000,000
Liabilities:
Derivative liabilities		894,000,000	1,138,000,000
Recurring Basis | Levels 1, 2 and 3 | Equity contracts
Assets:
Derivative assets		2,019,000,000	428,000,000
Liabilities:
Derivative liabilities		745,000,000	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		41,000,000	32,000,000
Liabilities:
Derivative liabilities		37,000,000	41,000,000
Recurring Basis | Levels 1, 2 and 3 | Other contracts
Assets:
Derivative assets		13,000,000	14,000,000
Liabilities:
Derivative liabilities		2,000,000
Recurring Basis | Levels 1, 2 and 3 | U.S. government and government sponsored entities
Assets:
Bonds available for sale		5,616,000,000	6,619,000,000
Recurring Basis | Levels 1, 2 and 3 | Obligations of states, municipalities and political subdivisions
Assets:
Bonds available for sale		10,663,000,000	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		12,453,000,000	13,485,000,000
Other bond securities, at fair value (See Note 5)		37,000,000	66,000,000
Recurring Basis | Levels 1, 2 and 3 | Corporate debt
Assets:
Bonds available for sale		138,432,000,000	137,839,000,000
Other bond securities, at fair value (See Note 5)		2,908,000,000	2,392,000,000
Recurring Basis | Levels 1, 2 and 3 | RMBS
Assets:
Bonds available for sale		20,444,000,000	18,817,000,000
Other bond securities, at fair value (See Note 5)		263,000,000	286,000,000
Recurring Basis | Levels 1, 2 and 3 | CMBS
Assets:
Bonds available for sale		14,128,000,000	14,193,000,000
Other bond securities, at fair value (See Note 5)		261,000,000	331,000,000
Recurring Basis | Levels 1, 2 and 3 | CLO/ABS
Assets:
Bonds available for sale		29,997,000,000	23,104,000,000
Other bond securities, at fair value (See Note 5)		1,681,000,000	1,299,000,000
Recurring Basis | Level 1
Assets:
Bonds available for sale		268,000,000	183,000,000
Other bond securities, at fair value (See Note 5)		0	0
Equity securities		632,000,000	518,000,000
Other invested assets		0	0
Derivative assets		7,000,000	12,000,000
Short-term investments		2,635,000,000	2,821,000,000
Market risk benefit assets, at fair value		0	0
Other assets		0	0
Separate account assets		87,814,000,000	81,655,000,000
Total(d)		91,356,000,000	85,189,000,000
Liabilities:
Policyholder contract deposits		0	0
Market risk benefit liabilities, at fair value		0	0
Derivative liabilities		2,000,000	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		2,000,000	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		7,000,000	11,000,000
Liabilities:
Derivative liabilities		2,000,000	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
Liabilities:
Derivative liabilities		0
Recurring Basis | Level 1 | U.S. government and government sponsored entities
Assets:
Bonds available for sale		35,000,000	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		233,000,000	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		204,621,000,000	201,074,000,000
Other bond securities, at fair value (See Note 5)		3,685,000,000	2,958,000,000
Equity securities		40,000,000	18,000,000
Other invested assets		155,000,000	145,000,000
Derivative assets		5,256,000,000	5,395,000,000
Short-term investments		8,137,000,000	2,887,000,000
Market risk benefit assets, at fair value		0	0
Other assets		0	0
Separate account assets		3,191,000,000	3,198,000,000
Total(d)		225,085,000,000	215,675,000,000
Liabilities:
Policyholder contract deposits		55,000,000	41,000,000
Market risk benefit liabilities, at fair value		0	0
Derivative liabilities		5,206,000,000	5,995,000,000
Fortitude Re funds withheld payable		0
Fortitude Re funds withheld payable			0
Other liabilities		107,000,000	0
Long-term debt		53,000,000	56,000,000
Total		5,421,000,000	6,092,000,000
Recurring Basis | Level 2 | Interest rate contracts
Assets:
Derivative assets		2,826,000,000	3,410,000,000
Liabilities:
Derivative liabilities		3,631,000,000	4,838,000,000
Recurring Basis | Level 2 | Foreign exchange contracts
Assets:
Derivative assets		1,235,000,000	1,844,000,000
Liabilities:
Derivative liabilities		891,000,000	1,138,000,000
Recurring Basis | Level 2 | Equity contracts
Assets:
Derivative assets		1,187,000,000	132,000,000
Liabilities:
Derivative liabilities		680,000,000	10,000,000
Recurring Basis | Level 2 | Commodity contracts
Assets:
Derivative assets			9,000,000
Recurring Basis | Level 2 | Credit contracts
Assets:
Derivative assets		8,000,000	0
Liabilities:
Derivative liabilities		4,000,000	9,000,000
Recurring Basis | Level 2 | Other contracts
Assets:
Derivative assets		0	0
Liabilities:
Derivative liabilities		0
Recurring Basis | Level 2 | U.S. government and government sponsored entities
Assets:
Bonds available for sale		5,581,000,000	6,594,000,000
Recurring Basis | Level 2 | Obligations of states, municipalities and political subdivisions
Assets:
Bonds available for sale		9,816,000,000	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		12,213,000,000	13,326,000,000
Other bond securities, at fair value (See Note 5)		37,000,000	66,000,000
Recurring Basis | Level 2 | Corporate debt
Assets:
Bonds available for sale		136,753,000,000	134,992,000,000
Other bond securities, at fair value (See Note 5)		2,697,000,000	1,976,000,000
Recurring Basis | Level 2 | RMBS
Assets:
Bonds available for sale		12,804,000,000	11,264,000,000
Other bond securities, at fair value (See Note 5)		105,000,000	113,000,000
Recurring Basis | Level 2 | CMBS
Assets:
Bonds available for sale		13,495,000,000	13,267,000,000
Other bond securities, at fair value (See Note 5)		244,000,000	303,000,000
Recurring Basis | Level 2 | CLO/ABS
Assets:
Bonds available for sale		13,959,000,000	10,356,000,000
Other bond securities, at fair value (See Note 5)		512,000,000	389,000,000
Recurring Basis | Level 3
Assets:
Bonds available for sale		26,844,000,000	24,899,000,000
Other bond securities, at fair value (See Note 5)		1,556,000,000	1,527,000,000
Equity securities		56,000,000	39,000,000
Other invested assets		2,070,000,000	2,075,000,000
Derivative assets		1,332,000,000	642,000,000
Short-term investments		0	0
Market risk benefit assets, at fair value		912,000,000	796,000,000
Other assets		243,000,000	107,000,000
Separate account assets		0	0
Total(d)		33,013,000,000	30,085,000,000
Liabilities:
Policyholder contract deposits		7,942,000,000	5,367,000,000
Market risk benefit liabilities, at fair value		5,705,000,000	4,736,000,000
Derivative liabilities		101,000,000	46,000,000
Fortitude Re funds withheld payable		(1,226,000,000)
Fortitude Re funds withheld payable			(2,235,000,000)
Other liabilities		122,000,000	112,000,000
Long-term debt		0	0
Total		12,644,000,000	8,026,000,000
Recurring Basis | Level 3 | Interest rate contracts
Assets:
Derivative assets		460,000,000	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		825,000,000	285,000,000
Liabilities:
Derivative liabilities		63,000,000	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		13,000,000	14,000,000
Liabilities:
Derivative liabilities		2,000,000
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		847,000,000	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		7,000,000	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		1,679,000,000	2,847,000,000
Other bond securities, at fair value (See Note 5)		211,000,000	416,000,000
Recurring Basis | Level 3 | RMBS
Assets:
Bonds available for sale		7,640,000,000	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		633,000,000	926,000,000
Other bond securities, at fair value (See Note 5)		17,000,000	28,000,000
Recurring Basis | Level 3 | CLO/ABS
Assets:
Bonds available for sale		16,038,000,000	12,748,000,000
Other bond securities, at fair value (See Note 5)		$ 1,169,000,000	$ 910,000,000

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