Income taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Current:
Federal	$ 0	$ 0	$ 0
State	45	183	63
Foreign	2,241	1,149	2,937
Total current income tax expense	2,286	1,332	3,000
Deferred:
Federal	0	0	0
State	0	0	0
Foreign	0	(149)	149
Total deferred income tax expense	0	(149)	149
Total provision for income taxes	$ 2,286	$ 1,183	$ 3,149