Insurance - Premiums receivable, 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
Premium Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ 9	$ 9	$ 8	$ 8
Provision (credit) for expected credit losses	0	(1)	1	0
Write-offs charged against the allowance	0	0	0	0
Ending Balance	13	8	13	8
Crop Risk Services
Premium Receivable, Allowance for Credit Loss [Roll Forward]
Increase in allowance from acquisition of CRS	$ 4	$ 0	$ 4	$ 0