Reinsurance, Allowance (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023
Reinsurance Disclosures [Abstract]
Valuation allowance for uncollectible reinsurance - beginning of period	$ 367	$ 351
Provision for uncollectible reinsurance	18	15
Write-offs charged against the valuation allowance	(3)	(6)
Foreign exchange revaluation	(1)	1
Valuation allowance for uncollectible reinsurance - end of period	$ 381	$ 361