Reinsurance, Allowance (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Reinsurance Disclosures [Abstract]
Valuation allowance for uncollectible reinsurance - beginning of period	$ 351	$ 329
Provision for uncollectible reinsurance	15	17
Write-offs charged against the valuation allowance	(6)	(4)
Foreign exchange revaluation	(1)	(1)
Valuation allowance for uncollectible reinsurance - end of period	$ 361	$ 341