Investments in debt and equity securities - Debt Securities According to Contractual Terms (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Amortized costs
In one year or less	$ 89,611
After one year through five years	318,078
After five years through ten years	166,600
After ten years	28,922
Amortized costs	603,211	$ 578,165
Fair values
In one year or less	90,044
After one year through five years	310,887
After five years through ten years	159,971
After ten years	28,494
Fair values	$ 589,396	$ 589,772