Reinsurance (Reinsurance Recoverable on Ceded Reinsurance) (Details) - USD ($) $ in Millions		Jun. 30, 2022	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2020
Reinsurance Disclosures [Abstract]
Reinsurance recoverable on unpaid losses and loss expenses	[1]	$ 16,573	$ 16,184	$ 14,721	$ 14,647
Reinsurance recoverable on paid losses and loss expenses	[1]	1,204	1,182
Reinsurance recoverable on losses and loss expenses	[1]	17,777	17,366
Reinsurance recoverable on policy benefits	[1]	205	213
Reinsurance Recoverables on Unpaid Losses, Allowance		283	271
Reinsurance Recoverables on Paid Losses, Allowance		58	58
Reinsurance Recoverable, Allowance for Credit Loss, Total		341	329	$ 322	$ 314
Reinsurance Recoverables on Future Policy Benefits, Allowance		$ 4	$ 4

[1] Net of valuation allowance for uncollectible reinsurance.