Investments Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Amortized Cost
Due in one year or less, Amortized Cost	$ 45,874
Due after one year through five years, Amortized Cost	246,621
Due after five years though ten years, Amortized Cost	374,788
Due after ten years through twenty years, Amortized Cost	52,592
Due after twenty years, Amortized Cost	1,262
Asset-backed securities, Amortized Cost	466,720
Totals, Amortized Cost	1,187,857	$ 1,189,951
Estimated Fair Value
Due in one year or less, Fair Value	45,844
Due after one year through five years, Fair Value	253,781
Due after five years through ten years, Fair Value	385,569
Due after ten years through twenty years, Fair Value	55,341
Due after twenty years, Fair Value	1,800
Asset-backed securities, Fair Value	475,944
Totals, Fair Value	$ 1,218,279	$ 1,256,653