Claim and Claim Adjustment Expense Reserves (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 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	$ 94	$ 114	$ 214	$ 171
Total pretax (favorable) unfavorable development	13	(17)	44	(2)
Retroactive reinsurance benefit recognized	15	17	38	40
Cumulative amounts ceded under AEP Loss Portfolio Transfer	3,500		3,500		$ 3,500
Hurricane Ian
Liability for Claims and Claims Adjustment Expense [Line Items]
Unusual or Infrequent Item, or Both, Net of Insurance Proceeds				87
Corporate & Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Total pretax (favorable) unfavorable development	20	$ 0	55	$ 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	388		388		$ 425
Fair value of collateral trust account established by NICO under A&EP Loss Portfolio Transfer	$ 2,300		$ 2,300