Reserve for Future Policy Benefits (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 479	$ 508	$ 484
Life Conversions
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	47	46	49	$ 47
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change	109	113	113	112
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax	(12)	(12)	(11)	(14)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance	121	125	124	126
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	2
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			125	128
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense	4	4
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment	(8)	(7)
Liability for Future Policy Benefit, before Reinsurance	$ 62	$ 67
Liability for Future Policy Benefit, Weighted-Average Duration	11 years 10 months 24 days	12 years 3 months 18 days
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	$ 201	$ 208
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	$ 111	$ 118
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate	4.20%	4.20%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate	5.30%	5.10%
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	$ 177	$ 192	185	192
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax	(35)	(35)	(32)	(39)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance	212	227	217	231
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			0	0
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			217	231
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense	2	2
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment	(7)	(6)
Liability for Future Policy Benefit, before Reinsurance	$ 177	$ 192
Liability for Future Policy Benefit, Weighted-Average Duration	6 years 3 months 18 days	6 years 6 months
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	$ 274	$ 295
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	5.20%	5.00%
Deferred Profit Liability
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 20	$ 19
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	135	143	137	140
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax	5	8	7	4
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance	130	135	130	136
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			$ 131	$ 136
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense	2	2
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment	(3)	(3)
Liability for Future Policy Benefit, before Reinsurance	$ 135	$ 143
Liability for Future Policy Benefit, Weighted-Average Duration	9 years	9 years 1 month 6 days
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	$ 255	$ 269
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	5.10%	5.00%
Long-Duration Insurance, Other
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 85	$ 87
Group Benefits
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Prior accident year development [1]	(189)	(133)
Group Benefits | Disability Insurance Policy [Member]
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Prior accident year development [1]	$ 149	$ 120