Investments in debt and equity securities - Debt Securities According to Contractual Terms (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Amortized costs
In one year or less	$ 90,765
After one year through five years	357,970
After five years through ten years	171,140
After ten years	15,372
Amortized costs	635,247	$ 646,728
Fair values
In one year or less	88,947
After one year through five years	337,352
After five years through ten years	162,291
After ten years	13,337
Fair values	$ 601,927	$ 611,934