Revenue - Revenue by discipline & geographical areas (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue
Total Revenue	$ 662,428	$ 474,560	$ 342,958
North America
Disaggregation of Revenue
Total Revenue	48,715	50,786	36,206
Asia Pacific
Disaggregation of Revenue
Total Revenue	516,105	385,233	251,020
Europe
Disaggregation of Revenue
Total Revenue	97,608	38,541	55,732
Systems
Disaggregation of Revenue
Total Revenue	454,598	293,624	202,571
Aftermarket
Disaggregation of Revenue
Total Revenue	$ 207,830	$ 180,936	$ 140,387