Market Risk Benefits - Market Risk Benefits In Asset and Liability Positions (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023	Dec. 31, 2022
Liability for Future Policy Benefit, Activity [Line Items]
Total market risk benefit assets	$ 2,499,234	$ 2,519,000	$ 2,367,243
Total market risk benefit liabilities	4,915,163	4,371,000	5,144,401
Variable Annuities
Liability for Future Policy Benefit, Activity [Line Items]
Net amount at risk	$ 7,321,371	$ 12,504,440
Weighted-average attained age of contractholders	71 years	70 years
Direct and assumed	$ 1,286,720	$ 1,410,637
Ceded	1,212,514	1,108,597
Total market risk benefit assets	2,499,234	2,519,234
Direct and assumed	4,653,521	4,087,498
Ceded	261,642	283,680
Total market risk benefit liabilities	4,915,163	4,371,178
Net liability	$ 2,415,929	$ 1,851,944	$ 3,694,950	$ 4,550,625