Property, plant and equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Property, plant and equipment
Total property, plant and equipment	$ 96,524	$ 81,540
Less accumulated depreciation	(44,383)	(38,904)
Net property, plant and equipment	52,141	42,636
Land
Property, plant and equipment
Total property, plant and equipment	2,378	1,500
Land improvements
Property, plant and equipment
Total property, plant and equipment	4,357	3,010
Leasehold Improvements
Property, plant and equipment
Total property, plant and equipment	2,569	859
Buildings
Property, plant and equipment
Total property, plant and equipment	26,058	24,476
Machinery and equipment
Property, plant and equipment
Total property, plant and equipment	40,878	35,628
Furniture and fixtures
Property, plant and equipment
Total property, plant and equipment	12,561	11,657
Mobile equipment and other
Property, plant and equipment
Total property, plant and equipment	3,873	2,255
Construction-in-process
Property, plant and equipment
Total property, plant and equipment	$ 3,850	$ 2,155