Property, plant and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Property, plant and equipment
Total property, plant and equipment	$ 124,717	$ 113,508
Less accumulated depreciation	(66,273)	(58,313)
Net property, plant and equipment	58,444	55,195
Land
Property, plant and equipment
Total property, plant and equipment	2,378	2,378
Land improvements
Property, plant and equipment
Total property, plant and equipment	4,541	4,357
Leasehold Improvements
Property, plant and equipment
Total property, plant and equipment	4,087	4,079
Buildings
Property, plant and equipment
Total property, plant and equipment	28,715	28,238
Machinery and equipment
Property, plant and equipment
Total property, plant and equipment	55,238	50,129
Furniture and fixtures
Property, plant and equipment
Total property, plant and equipment	17,918	16,360
Mobile equipment and other
Property, plant and equipment
Total property, plant and equipment	5,285	4,883
Construction-in-process
Property, plant and equipment
Total property, plant and equipment	$ 6,555	$ 3,084