Future Policy Benefits - Schedule of Balances and Changes in the Deferred Profit Liability (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Immediate Annuities
Deferred Profit Liability Rollforward [Roll Forward]
Balance, beginning of year	$ 87	$ 69
Effect of modeling changes		0	$ 4
Effect of changes in cash flow assumptions		0	0
Effect of actual variances from expected experience		6	16
Balance adjusted for variances from expectation		93	89
Issuances	2	3
Interest accrual	1	2
Amortization	(6)	(7)
Balance, end of period	90	87
Effect of modeling changes		0	4
Effect of changes in cash flow assumptions		0	0
Effect of actual variances from expected experience		6	16
PRT
Deferred Profit Liability Rollforward [Roll Forward]
Balance, beginning of year	10	4
Effect of modeling changes		0	0
Effect of changes in cash flow assumptions		(7)	1
Effect of actual variances from expected experience		0	5
Balance adjusted for variances from expectation		3	10
Issuances	0	0
Interest accrual	4	1
Amortization	(1)	(1)
Balance, end of period	$ 6	10
Effect of modeling changes		0	0
Effect of changes in cash flow assumptions		(7)	1
Effect of actual variances from expected experience		$ 0	$ 5