Unpaid losses and loss expenses (RF) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2022 USD ($)		Sep. 30, 2021 USD ($)
Unpaid Losses and Loss Expenses [Roll Forward]
Gross unpaid losses and loss expenses – beginning of period	$ 72,943		$ 67,811
Reinsurance recoverable on unpaid losses – beginning of period (1)	(16,184)	[1]	(14,647)	[1]
Net unpaid losses and loss expenses – beginning of period	56,759		53,164
Current Year Claims and Claims Adjustment Expense	18,426		17,556
Prior Year Claims and Claims Adjustment Expense	(952)	[2]	(868)	[2]
Total, Incurred	17,474		16,688
Net loss and loss expenses paid, Current Year	5,104		4,771
Net loss and loss expenses paid, Prior Years	9,217		7,922
Total, Paid	14,321		12,693
Liability For Unpaid Claims And Claims Adjustment Expense Foreign Currency Revaluation And Other	(1,300)		(78)
Net unpaid losses and loss expenses – end of period	58,612		57,081
Reinsurance recoverable on unpaid losses (1)	17,380	[1]	15,550	[1]
Gross unpaid losses and loss expenses – end of period	75,992		72,631
prior period development, net adjustments	243		$ 87
Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease), Gross	3,049
Liability for Unpaid Claims and Claims Adjustment Expense, Period Increase (Decrease)	$ 1,853

[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, and earned premiums totaling $243 million and $87 million for the nine months ended September 30, 2022 and 2021, respectively.