Market Risk Benefits - Market Risk Benefits In Asset and Liability Positions (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Dec. 31, 2023
Liability for Future Policy Benefit, Activity [Line Items]
Direct and assumed	$ 1,337,768	$ 1,286,720
Ceded	1,246,942	1,212,514
Total market risk benefit assets	2,584,710	2,499,234	$ 2,637,363
Direct and assumed	4,356,868	4,653,521
Ceded	261,465	261,642
Total market risk benefit liabilities	4,618,333	4,915,163	4,281,244
Net liability	2,033,623	2,415,929
Variable Annuities
Liability for Future Policy Benefit, Activity [Line Items]
Net amount at risk	$ 7,533,650	$ 7,321,371
Weighted-average attained age of contractholders	72 years	71 years
Direct and assumed	$ 1,333,060	$ 1,286,720
Ceded	1,246,942	1,212,514
Total market risk benefit assets	2,580,002	2,499,234
Direct and assumed	4,148,385	4,653,521
Ceded	261,465	261,642
Total market risk benefit liabilities	4,409,850	4,915,163
Net liability	1,829,848	2,415,929	$ 2,488,463	$ 3,707,407
Fixed Annuities
Liability for Future Policy Benefit, Activity [Line Items]
Net amount at risk	$ 486,180
Weighted-average attained age of contractholders	66 years
Direct and assumed	$ 4,708	0
Ceded	0	0
Total market risk benefit assets	4,708	0
Direct and assumed	208,483	0
Ceded	0	0
Total market risk benefit liabilities	208,483	0
Net liability	$ 203,775	$ 0