Claim and Claim Adjustment Expense Reserves (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022	Dec. 31, 2010
Liability for Claims and Claims Adjustment Expense [Line Items]
Unusual or Infrequent Item, or Both, Net of Insurance Proceeds	$ 68	$ 37	$ 120	$ 57
Total pretax (favorable) unfavorable development	18	27	31	15
Retroactive reinsurance benefit recognized	15	11	23	23
Cumulative amounts ceded under AEP Loss Portfolio Transfer	3,500		3,500		$ 3,500
Corporate & Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Total pretax (favorable) unfavorable development	35	$ 64	35	$ 64
Asbestos and Environmental Reserves
Liability for Claims and Claims Adjustment Expense [Line Items]
Net A&EP claim and allocated claim adjustment expense reserves ceded to NICO						$ 1,600
Aggregate limit under A&EP Loss Portfolio Transfer						4,000
A&EP claim and allocated claim adjustment expense reserves ceded under existing third party reinsurance contracts transferred to NICO under A&EP Loss Portfolio Transfer						1,200
Reinsurance premium paid to NICO under A&EP Loss Portfolio Transfer						2,000
Net reinsurance receivables transferred to NICO under A&EP Loss Portfolio Transfer						215
Total consideration paid to NICO under AEP Loss Portfolio Transfer						$ 2,200
Deferred reinsurance benefit yet to be recognized	402		402		$ 425
Fair value of collateral trust account established by NICO under A&EP Loss Portfolio Transfer	$ 2,400		$ 2,400