Investments Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Amortized Cost
Due in one year or less, Amortized Cost	$ 46,850
Due after one year through five years, Amortized Cost	309,662
Due after five years though ten years, Amortized Cost	306,656
Due after ten years through twenty years, Amortized Cost	83,872
Due after twenty years, Amortized Cost	846
Asset-backed securities, Amortized Cost	444,471
Totals, Amortized Cost	1,192,357	$ 1,175,413
Estimated Fair Value
Due in one year or less, Fair Value	47,146
Due after one year through five years, Fair Value	317,821
Due after five years through ten years, Fair Value	321,000
Due after ten years through twenty years, Fair Value	87,952
Due after twenty years, Fair Value	961
Asset-backed securities, Fair Value	453,160
Totals, Fair Value	$ 1,228,040	$ 1,161,862