Insurance - Recoverables from reinsurance, progression of allowance for expected credit losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 9	$ 7	$ 8	$ 8
Provision (credit) for expected credit losses	2	1	3	0
Write-offs charged against the allowance	0	0	0	0
Ending Balance	11	8	11	8
Crop Risk Services
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Increase in allowance from acquisition of CRS	$ 0	$ 0	$ 0	$ 0