Reinsurance, Allowance (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reinsurance Disclosures [Abstract]
Valuation allowance for uncollectible reinsurance	$ 329	$ 314	$ 316
Provision for uncollectible reinsurance	66	21
Write-offs charged against the valuation allowance	(50)	(25)
Foreign exchange revaluation	$ (1)	$ 2