Investments - Amortized Cost and Estimated Fair Value of Available-For-Sale Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Amortized cost
Due in one year or less	$ 46,013
Due after one year through five years	401,680
Due after five years through ten years	204,733
Due after ten years	297,158
Amortized cost	949,584	$ 938,279
Estimated fair value
Due in one year or less	46,104
Due after one year through five years	392,696
Due after five years through ten years	200,244
Due after ten years	284,276
Estimated fair value	$ 923,320	$ 946,085