Future Policy Benefit Reserves - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2025	Dec. 31, 2024
Insurance [Abstract]
Liability for unpaid claims and claims adjustment expense, long term care policies, period increase (decrease)	$ 7	$ 15
Liability for future policy benefit, expected future gross premium, discounted, before reinsurance			$ 3,507	$ 3,573
Liability for future policy benefit, weighted-average duration			11 years	11 years
Liability future policy benefit, losses recognized in current period			$ 135	$ 159
Liability future policy benefit, losses recognized in prior period			$ 58	$ 29