Reserve for Future Policy Benefits (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 456	$ 470	$ 448
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	126	135	128	$ 137
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax	4	8	0	7
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance	122	127	128	130
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)	1
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			127	131
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense	4	5
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment	(9)	(9)
Liability for Future Policy Benefit, before Reinsurance	$ 126	$ 135
Liability for Future Policy Benefit, Weighted-Average Duration	9 years 4 months 24 days	9 years
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	$ 240	$ 249
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	5.20%	4.90%
Life Conversions
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, Expected Future Gross Premium, Discounted, before Reinsurance	$ 43	$ 46	45	48
Liability for Future Policy Benefit, Expected Future Policy Benefit, before Reinsurance, after Discount Rate Change	105	112	106	113
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax	(13)	(10)	(15)	(11)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance	118	122	121	124
Liability for Future Policy Benefit, Expected Net Premium, Cumulative Increase (Decrease) from Cash Flow Change			0	2
Liability for Future Policy Benefit, Expected Future Policy Benefit, Cumulative Increase (Decrease) of Actual Variance from Expected Experience			3	3
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			124	129
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense	15	16
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment	(21)	(23)
Liability for Future Policy Benefit, before Reinsurance	$ 62	$ 66
Liability for Future Policy Benefit, Weighted-Average Duration	11 years	11 years 7 months 6 days
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	$ 189	$ 199
Liability for Future Policy Benefit, Expected Future Gross Premium, Undiscounted, before Reinsurance	$ 100	$ 107
Liability for Future Policy Benefit, Weighted-Average Interest Accretion Rate	4.30%	4.30%
Liability for Future Policy Benefit, Current Weighted-Average Discount Rate	5.40%	5.00%
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	$ 167	$ 176	168	185
AOCI, Liability for Future Policy Benefit, Expected Future Policy Benefit, before Tax	(24)	(26)	(33)	(32)
Liability for Future Policy Benefit, Expected Future Policy Benefit, Original Discount Rate, before Cash Flow and Reinsurance	191	202	201	217
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			1	(1)
Liability for Future Policy Benefit, Expected Future Benefit, Original Discount Rate, before Reinsurance, after Cash Flow Change			$ 203	$ 216
Liability for Future Policy Benefit, Expected Future Policy Benefit, Interest Expense	4	5
Liability for Future Policy Benefit, Expected Future Policy Benefit, Benefit Payment	(16)	(19)
Liability for Future Policy Benefit, before Reinsurance	$ 167	$ 176
Liability for Future Policy Benefit, Weighted-Average Duration	6 years 2 months 12 days	6 years 7 months 6 days
Liability for Future Policy Benefit, Expected Future Policy Benefit, Undiscounted, before Reinsurance	$ 244	$ 262
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	4.80%	4.70%
Deferred Profit Liability
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 16	$ 19
Long-Duration Insurance, Other
Liabilities for Guarantees on Long-Duration Contracts [Line Items]
Liability for Future Policy Benefit, before Reinsurance	$ 85	$ 74