Investments Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Amortized Cost
Due in one year or less, Amortized Cost	$ 94,472
Due after one year through five years, Amortized Cost	288,475
Due after five years though ten years, Amortized Cost	309,350
Due after ten years through twenty years, Amortized Cost	86,213
Due after twenty years, Amortized Cost	1,643
Asset-backed securities, Amortized Cost	386,627
Totals, Amortized Cost	1,166,780	$ 1,192,357
Estimated Fair Value
Due in one year or less, Fair Value	95,498
Due after one year through five years, Fair Value	298,896
Due after five years through ten years, Fair Value	328,829
Due after ten years through twenty years, Fair Value	90,188
Due after twenty years, Fair Value	1,905
Asset-backed securities, Fair Value	409,841
Totals, Fair Value	$ 1,225,157	$ 1,228,040