Investments - Unrealized Losses (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Cost or amortized Cost
Total Cost or Amortized Cost	$ 2,753,939	$ 2,694,739
Fair value
Total Fair Value	2,493,000	2,414,517
Unrealized Loss
Total Unrealized Loss	$ (260,939)	$ (280,222)
Percent to Total	100.00%
NAIC Rating 1 | AAA/AA/A | Aaa/Aa/A
Cost or amortized Cost
Total Cost or Amortized Cost	$ 2,269,819
Fair value
Total Fair Value	2,052,151
Unrealized Loss
Total Unrealized Loss	$ (217,668)
Percent to Total	83.40%
NAIC Rating 2 | BBB | Baa
Cost or amortized Cost
Total Cost or Amortized Cost	$ 404,162
Fair value
Total Fair Value	366,729
Unrealized Loss
Total Unrealized Loss	$ (37,433)
Percent to Total	14.40%
NAIC Rating 3 | BB | Ba
Cost or amortized Cost
Total Cost or Amortized Cost	$ 45,298
Fair value
Total Fair Value	41,464
Unrealized Loss
Total Unrealized Loss	$ (3,834)
Percent to Total	1.50%
NAIC Rating 4 | B | B
Cost or amortized Cost
Total Cost or Amortized Cost	$ 32,264
Fair value
Total Fair Value	30,844
Unrealized Loss
Total Unrealized Loss	$ (1,420)
Percent to Total	0.50%
NAIC Rating 5 | CCC | Caa
Cost or amortized Cost
Total Cost or Amortized Cost	$ 2,396
Fair value
Total Fair Value	1,812
Unrealized Loss
Total Unrealized Loss	$ (584)
Percent to Total	0.20%
NAIC Rating 6 | CC Or Lower | Ca or lower
Unrealized Loss
Percent to Total	0.00%