Reinsurance and indemnification - Rollforward of credit loss allowance for reinsurance recoverables (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Property-Liability
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ (66)	$ (59)
Increase (decrease) in the provision for credit losses	0	(1)
Write-offs	0	0
Ending balance	(66)	(60)
Accident and health insurance
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Beginning balance	(8)	(1)
Increase (decrease) in the provision for credit losses	0	0
Write-offs	0	0
Ending balance	$ (8)	$ (1)