Unpaid losses and loss expenses (RF) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023
Liability for Claims and Claims Adjustment Expense [Line Items]
Gross unpaid losses and loss expenses – beginning of period		$ 80,122	$ 75,747
Reinsurance recoverable on unpaid losses and loss expenses – beginning of period (1)	[1]	(17,884)	(17,086)
Net unpaid losses and loss expenses – beginning of period		62,238	58,661
Current Year Claims and Claims Adjustment Expense		20,302	18,604
Prior Year Claims and Claims Adjustment Expense	[2]	(761)	(667)
Total, Incurred		19,541	17,937
Net loss and loss expenses paid, Current Year		5,005	4,853
Net loss and loss expenses paid, Prior Years		10,074	10,158
Total, Paid		15,079	15,011
Foreign currency revaluation and other		(5)	(95)
Net unpaid losses and loss expenses – end of period		66,695	61,897
Reinsurance recoverable on unpaid losses and loss expenses (1)	[1]	17,631	17,808
Gross unpaid losses and loss expenses – end of period		84,326	79,705
prior period development, net adjustments		118	71
Huatai Group
Liability for Claims and Claims Adjustment Expense [Line Items]
Net unpaid losses and loss expenses – end of period		$ 0	$ 405

[1] Net of valuation allowance for uncollectible reinsurance.

[2] Relates to prior period loss reserve development only and excludes prior period development related to reinstatement premiums, expense adjustments, earned premiums, and A&H long-duration lines totaling $118 million and $71 million for the nine months ended September 30, 2024 and 2023, respectively.