Investments - Unrealized Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2025	Dec. 31, 2024
Cost or amortized Cost
Total Cost or Amortized Cost	$ 2,066,699	$ 2,768,205
Fair value
Total Fair Value	1,916,331	2,543,594
Unrealized Loss
Total Unrealized Loss	$ (150,368)	$ (224,611)
Percent to Total	100.00%
NAIC Rating 1 | AAA/AA/A | Aaa/Aa/A
Cost or amortized Cost
Total Cost or Amortized Cost	$ 1,675,642
Fair value
Total Fair Value	1,539,255
Unrealized Loss
Total Unrealized Loss	$ (136,387)
Percent to Total	90.70%
NAIC Rating 2 | BBB | Baa
Cost or amortized Cost
Total Cost or Amortized Cost	$ 327,018
Fair value
Total Fair Value	315,660
Unrealized Loss
Total Unrealized Loss	$ (11,358)
Percent to Total	7.60%
NAIC Rating 3 | BB | Ba
Cost or amortized Cost
Total Cost or Amortized Cost	$ 32,804
Fair value
Total Fair Value	32,154
Unrealized Loss
Total Unrealized Loss	$ (650)
Percent to Total	0.40%
NAIC Rating 4 | B | B
Cost or amortized Cost
Total Cost or Amortized Cost	$ 26,763
Fair value
Total Fair Value	25,279
Unrealized Loss
Total Unrealized Loss	$ (1,484)
Percent to Total	1.00%
NAIC Rating 5 | CCC | Caa
Cost or amortized Cost
Total Cost or Amortized Cost	$ 3,652
Fair value
Total Fair Value	3,330
Unrealized Loss
Total Unrealized Loss	$ (322)
Percent to Total	0.20%
NAIC Rating 6 | CC Or Lower | Ca or lower
Cost or amortized Cost
Total Cost or Amortized Cost	$ 820
Fair value
Total Fair Value	653
Unrealized Loss
Total Unrealized Loss	$ (167)
Percent to Total	0.10%