Investments, Debt Securities, Amortized Cost and Fair Value by Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Available-for-Sale Debt Securities, Amortized Cost [Abstract]
Due in one year or less	$ 19,997
Due after one year through five years	68,523
Due after five years through ten years	82,046
Due after ten years	147,878
Amortized cost	318,444	$ 287,521
Available-for-Sale Debt Securities, Fair Value [Abstract]
Due in one year or less	20,279
Due after one year through five years	70,801
Due after five years through ten years	82,528
Due after ten years	148,359
Fair value	$ 321,967	$ 295,189