Investments - Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Cost or amortized Cost
Total Cost or Amortized Cost	$ 2,436,518	$ 2,768,205
Fair value
Total Fair Value	2,246,882	2,543,594
Unrealized Loss
Total Unrealized Loss	$ (189,636)	$ (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	$ 1,965,187
Fair value
Total Fair Value	1,798,753
Unrealized Loss
Total Unrealized Loss	$ (166,434)
Percent to Total	87.70%
NAIC Rating 2 | BBB | Baa
Cost or amortized Cost
Total Cost or Amortized Cost	$ 372,593
Fair value
Total Fair Value	353,280
Unrealized Loss
Total Unrealized Loss	$ (19,313)
Percent to Total	10.20%
NAIC Rating 3 | BB | Ba
Cost or amortized Cost
Total Cost or Amortized Cost	$ 54,671
Fair value
Total Fair Value	53,401
Unrealized Loss
Total Unrealized Loss	$ (1,270)
Percent to Total	0.70%
NAIC Rating 4 | B | B
Cost or amortized Cost
Total Cost or Amortized Cost	$ 39,947
Fair value
Total Fair Value	38,104
Unrealized Loss
Total Unrealized Loss	$ (1,843)
Percent to Total	1.00%
NAIC Rating 5 | CCC | Caa
Cost or amortized Cost
Total Cost or Amortized Cost	$ 3,300
Fair value
Total Fair Value	2,871
Unrealized Loss
Total Unrealized Loss	$ (429)
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	473
Unrealized Loss
Total Unrealized Loss	$ (347)
Percent to Total	0.20%