Reinsurance, Allowance (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Reinsurance Disclosures [Abstract]
Valuation allowance for uncollectible reinsurance - beginning of period	$ 367	$ 351
Provision for uncollectible reinsurance	24	27
Write-offs charged against the valuation allowance	(4)	(8)
Foreign exchange revaluation	1	0
Valuation allowance for uncollectible reinsurance - end of period	$ 388	$ 370