Property, plant and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, plant and equipment
Total property, plant and equipment	$ 113,508	$ 104,959
Less accumulated depreciation	(58,313)	(50,997)
Net property, plant and equipment	55,195	53,962
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	4,357	4,357
Leasehold Improvements
Property, plant and equipment
Total property, plant and equipment	4,079	4,183
Buildings
Property, plant and equipment
Total property, plant and equipment	28,238	26,846
Machinery and equipment
Property, plant and equipment
Total property, plant and equipment	50,129	44,618
Furniture and fixtures
Property, plant and equipment
Total property, plant and equipment	16,360	13,681
Mobile equipment and other
Property, plant and equipment
Total property, plant and equipment	4,883	4,576
Construction-in-process
Property, plant and equipment
Total property, plant and equipment	$ 3,084	$ 4,320