Reserve for Future Policy Benefits (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2021	Dec. 31, 2020
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 463	$ 508	$ 502	$ 646	$ 723	$ 638
Life Conversions
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	46	47	47	58
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change	105	114	112	152
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax	(20)	(16)	(14)	19
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance	125	130	126	133
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			1	0
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			4	5
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			131	138
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense	14	13
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment	(20)	(21)
Liability for Future Policy Benefit, before Reinsurance	$ 59	$ 67				94
Liability for Future Policy Benefit, Weighted-Average Duration	11 years 4 months 24 days	12 years
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	$ 206	$ 217
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	$ 116	$ 125
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate	4.20%	4.10%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate	5.90%	5.40%
Paid Up Life
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change	$ 176	$ 193	192	262
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax	(44)	(41)	(39)	14
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance	220	234	231	248
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			0	0
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			(1)	0
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			230	248
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense	7	5
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment	(17)	(19)
Liability for Future Policy Benefit, before Reinsurance	$ 176	$ 193				267
Liability for Future Policy Benefit, Weighted-Average Duration	6 years 1 month 6 days	6 years 4 months 24 days
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	$ 285	$ 305
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	$ 0	$ 0
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate	2.90%	2.90%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate	5.90%	5.30%
Deferred Profit Liability
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 20	$ 19				0
Fixed Annuity
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change	128	139	140	188
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax	(3)	1	4	47
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance	131	138	136	141
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			(2)	0
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			1	0
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			$ 135	$ 141
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense	5	6
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment	(9)	(9)
Liability for Future Policy Benefit, before Reinsurance	$ 128	$ 139				189
Liability for Future Policy Benefit, Weighted-Average Duration	9 years	9 years 2 months 12 days
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	$ 259	$ 275
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	$ 0	$ 0
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate	5.60%	5.60%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate	5.90%	5.50%
Long-Duration Insurance, Other
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 80	$ 90				$ 88
Group Benefits
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Prior accident year development	(403)	(323)
Group Benefits | Disability Insurance Policy [Member]
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Prior accident year development	$ 369	$ 275