Insurance - Recoverables from reinsurance, progression of allowance for expected credit losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 10	$ 9	$ 10	$ 8
Provision (credit) for expected credit losses	0	2	0	3
Write-offs charged against the allowance	0	0	0	0
Ending Balance	10	11	10	11
Crop Risk Services
Reinsurance Recoverable, Allowance for Credit Loss [Roll Forward]
Increase in allowance from acquisition of CRS	$ 0	$ 0	$ 0	$ 0