Investments - Unrealized Losses (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Cost or amortized Cost
Total Cost or Amortized Cost	$ 2,527,657	$ 2,694,739
Fair value
Total Fair Value	2,291,983	2,414,517
Unrealized Loss
Total Unrealized Loss	$ (235,674)	$ (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	$ 2,031,998
Fair value
Total Fair Value	1,837,626
Unrealized Loss
Total Unrealized Loss	$ (194,372)
Percent to Total	82.50%
NAIC Rating 2 | BBB | Baa
Cost or amortized Cost
Total Cost or Amortized Cost	$ 396,016
Fair value
Total Fair Value	360,851
Unrealized Loss
Total Unrealized Loss	$ (35,165)
Percent to Total	14.90%
NAIC Rating 3 | BB | Ba
Cost or amortized Cost
Total Cost or Amortized Cost	$ 58,153
Fair value
Total Fair Value	54,496
Unrealized Loss
Total Unrealized Loss	$ (3,657)
Percent to Total	1.60%
NAIC Rating 4 | B | B
Cost or amortized Cost
Total Cost or Amortized Cost	$ 38,897
Fair value
Total Fair Value	37,168
Unrealized Loss
Total Unrealized Loss	$ (1,729)
Percent to Total	0.70%
NAIC Rating 5 | CCC | Caa
Cost or amortized Cost
Total Cost or Amortized Cost	$ 2,593
Fair value
Total Fair Value	1,842
Unrealized Loss
Total Unrealized Loss	$ (751)
Percent to Total	0.30%
NAIC Rating 6 | Standard Poors CC Or Lower Member | Ca
Unrealized Loss
Percent to Total	0.00%