Claim and Claim Adjustment Expense Reserves (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Dec. 31, 2010
Liability for Claims and Claims Adjustment Expense [Line Items]
Unusual or infrequent item, or both, net of insurance proceeds	$ 37	$ 54	$ 57	$ 179
Pretax (favorable) unfavorable premium development, excluding Life & Group	27	29	15	14
Retroactive reinsurance benefit recognized	11	12	23	22
Corporate & Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Pretax (favorable) unfavorable premium development, excluding Life & Group	64	$ 40	64	$ 40
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
Cumulative amounts ceded under AEP Loss Portfolio Transfer	3,400		3,400		$ 3,400
Deferred reinsurance benefit yet to be recognized	406		406		$ 429
Fair value of collateral trust account established by NICO under A&EP Loss Portfolio Transfer	$ 2,400		$ 2,400