Investments in debt and equity securities - Debt Securities According to Contractual Terms (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Amortized costs
In one year or less	$ 98,843
After one year through five years	333,202
After five years through ten years	158,609
After ten years	32,960
Amortized costs	623,614	$ 578,165
Fair values
In one year or less	98,429
After one year through five years	318,895
After five years through ten years	145,799
After ten years	30,460
Fair values	$ 593,583	$ 589,772