Investments - Amortized Cost and Estimated Fair Value of Available-For-Sale Securities by Contractual Maturity (Details) $ in Thousands	Dec. 31, 2021 USD ($)
Amortized cost
Due in one year or less	$ 38,061
Due after one year through five years	409,379
Due after five years through ten years	195,937
Due after ten years	294,902
Amortized cost	938,279
Estimated fair value
Due in one year or less	38,396
Due after one year through five years	414,588
Due after five years through ten years	197,733
Due after ten years	295,368
Estimated fair value	$ 946,085