Investments Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Amortized Cost
Due in one year or less, Amortized Cost	$ 67,468
Due after one year through five years, Amortized Cost	300,404
Due after five years though ten years, Amortized Cost	306,192
Due after ten years through twenty years, Amortized Cost	87,050
Due after twenty years, Amortized Cost	1,854
Asset-backed securities, Amortized Cost	405,698
Totals, Amortized Cost	1,168,666	$ 1,192,357
Estimated Fair Value
Due in one year or less, Fair Value	68,303
Due after one year through five years, Fair Value	308,520
Due after five years through ten years, Fair Value	321,694
Due after ten years through twenty years, Fair Value	90,948
Due after twenty years, Fair Value	2,063
Asset-backed securities, Fair Value	428,186
Totals, Fair Value	$ 1,219,714	$ 1,228,040