Investments in debt and equity securities - Debt Securities According to Contractual Terms (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Amortized costs
In one year or less	$ 63,817
After one year through five years	380,826
After five years through ten years	174,554
After ten years	15,419
Amortized costs	634,616	$ 646,728
Fair values
In one year or less	63,214
After one year through five years	363,161
After five years through ten years	168,393
After ten years	13,546
Fair values	$ 608,314	$ 611,934