Summary of significant accounting policies - Disaggregated Net Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenues	$ 46,931	$ 38,755	$ 88,085	$ 70,965
Revenues recognized over time
Disaggregation of Revenue [Line Items]
Total revenues	46,931	36,790	88,085	68,156
Revenues recognized at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 0	$ 1,965	$ 0	$ 2,809