Investments - Amortized Cost and Estimated Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Amortized Cost
Due in one year or less, Amortized Cost	$ 4,899
Due after one year through five years, Amortized Cost	289,109
Due after five years though ten years, Amortized Cost	328,816
Due after ten years through twenty years, Amortized Cost	38,044
Due after twenty years, Amortized Cost	1,570
Asset-backed securities, Amortized Cost	490,341
Totals, Amortized Cost	1,152,779	$ 1,187,857
Estimated Fair Value
Due in one year or less, Fair Value	4,665
Due after one year through five years, Fair Value	269,852
Due after five years through ten years, Fair Value	296,368
Due after ten years through twenty years, Fair Value	34,623
Due after twenty years, Fair Value	1,483
Asset-backed securities, Fair Value	443,164
Totals, Fair Value	$ 1,050,155	$ 1,218,279