Claim and Claim Adjustment Expense Reserves and Future Policy Benefit Reserves (Narrative) (Details) - USD ($)		3 Months Ended			9 Months Ended	12 Months Ended			13 Months Ended
	Feb. 05, 2021	Sep. 30, 2022	Sep. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Feb. 05, 2021	Dec. 31, 2010
Liability for Claims and Claims Adjustment Expense [Line Items]
Pretax (favorable) unfavorable premium development, excluding Life & Group						$ (32,000,000)	$ 11,000,000	$ (20,000,000)
Funds held under reinsurance agreements, liability	$ 690,000,000					3,700,000,000	4,000,000,000		$ 690,000,000
Retroactive reinsurance agreement, maximum	1,000,000,000								1,000,000,000
Reinsurance premiums paid	$ 697,000,000								$ 64,000,000
Reinsurance, loss on uncollectible accounts in period, amount				$ 12,000,000
Securities held as collateral, at fair value						608,000,000
Liability for unpaid claims and claims adjustment expense, long term care policies, period increase (decrease)		$ (25,000,000)	$ (40,000,000)
Gross IBNR reserves		107,000,000			$ 107,000,000	14,712,000,000	13,619,000,000
Liability for unpaid claims and claims adjustment expense, claim severity adjustment, period increase (decrease)		(82,000,000)			(82,000,000)
Liability for unpaid claims and claims adjustment expense structured settlement obligations period increase (decrease)		(5,000,000)	2,000,000
Liability for future policy benefits, gross premium valuation, pretax margin		$ 125,000,000	$ 72,000,000		$ 125,000,000
Corporate & Other
Liability for Claims and Claims Adjustment Expense [Line Items]
Pretax (favorable) unfavorable premium development, excluding Life & Group						64,000,000	60,000,000	50,000,000
Gross IBNR reserves						1,321,000,000	1,266,000,000
Commercial
Liability for Claims and Claims Adjustment Expense [Line Items]
Pretax (favorable) unfavorable premium development, excluding Life & Group						(43,000,000)	(6,000,000)	(7,000,000)
Gross IBNR reserves						6,239,000,000	5,706,000,000
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										$ 1,600,000,000
Aggregate limit under A&EP Loss Portfolio Transfer										4,000,000,000
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										1,200,000,000
Reinsurance premium paid to NICO under A&EP Loss Portfolio Transfer										2,000,000,000
Net reinsurance receivables transferred to NICO under A&EP Loss Portfolio Transfer										215,000,000
Total consideration paid to NICO under AEP Loss Portfolio Transfer										$ 2,200,000,000
Net A&EP adverse development before consideration of LPT						92,000,000	143,000,000	125,000,000
Provision for uncollectible third-party reinsurance, released						5,000,000	5,000,000	$ 25,000,000
Cumulative amounts ceded under AEP Loss Portfolio Transfer						3,500,000,000	3,400,000,000
Deferred reinsurance benefit yet to be recognized						425,000,000	$ 429,000,000
Fair value of collateral trust account established by NICO under A&EP Loss Portfolio Transfer						2,400,000,000
Excess Workers' Compensation LPT
Liability for Claims and Claims Adjustment Expense [Line Items]
Funds held under reinsurance agreements, liability						$ 690,000,000