Policyholders' account balances (Policyholder Account Balance Rollforward) (Details) - USD ($) $ in Millions				9 Months Ended
		Jul. 01, 2023	Jul. 01, 2022	Sep. 30, 2023	Sep. 30, 2022
Policyholder Account Balance [Line Items]
Policyholder Account Balance, Beginning Balance				$ 3,140	$ 2,766
Policyholder Account Balance, Consolidation of Huatai Group		$ 4,014
Policyholder Account Balance, Acquisition of Cigna			$ 355
Policyholder Account Balance, Premium Received				503	347
Policyholder Account Balance, Policy Charge	[1]			(143)	(149)
Policyholder Account Balance, Surrender and Withdrawal				(182)	(94)
Policyholder Account Balance, Benefit Payment				(87)	(18)
Policyholder Account Balance, Interest Expense				82	55
Policyholder Account Balance, Increase (Decrease) from Other Change				(149)	254
Policyholder Account Balance, Ending Balance				7,178	3,008
Universal Life
Policyholder Account Balance [Line Items]
Policyholder Account Balance, Beginning Balance				1,719	1,612
Policyholder Account Balance, Consolidation of Huatai Group		602
Policyholder Account Balance, Acquisition of Cigna			10
Policyholder Account Balance, Premium Received				275	292
Policyholder Account Balance, Policy Charge	[1]			(135)	(141)
Policyholder Account Balance, Surrender and Withdrawal				(69)	(55)
Policyholder Account Balance, Benefit Payment				(6)	(3)
Policyholder Account Balance, Interest Expense				39	30
Policyholder Account Balance, Increase (Decrease) from Other Change				(42)	69
Policyholder Account Balance, Ending Balance				$ 2,383	$ 1,676
Policyholder Account Balance, Weighted Average Crediting Rate				3.80%	3.70%
Policyholder Account Balance, Net Amount at Risk	[2]			$ 10,493	$ 10,116
Policyholder Account Balance, Cash Surrender Value				1,596	934
Insurance, Other
Policyholder Account Balance [Line Items]
Policyholder Account Balance, Beginning Balance				1,421	1,154
Policyholder Account Balance, Consolidation of Huatai Group		$ 3,412
Policyholder Account Balance, Acquisition of Cigna			$ 345
Policyholder Account Balance, Premium Received				228	55
Policyholder Account Balance, Policy Charge	[1]			(8)	(8)
Policyholder Account Balance, Surrender and Withdrawal				(113)	(39)
Policyholder Account Balance, Benefit Payment				(81)	(15)
Policyholder Account Balance, Interest Expense				43	25
Policyholder Account Balance, Increase (Decrease) from Other Change				(107)	185
Policyholder Account Balance, Ending Balance				$ 4,795	$ 1,332
Policyholder Account Balance, Weighted Average Crediting Rate				2.10%	2.60%
Policyholder Account Balance, Net Amount at Risk	[2]			$ 1,675	$ 1,503
Policyholder Account Balance, Cash Surrender Value				$ 3,655	$ 1,280

[1] Contracts included in the policyholder account balances are generally charged a premium and/or monthly assessments on the basis of the account balance

[2] For those guarantees of benefits that are payable in the event of death, the net amount at risk is defined as the current guaranteed minimum death benefit in excess of the current account balance at the balance sheet date.