Product Warranties (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Product Warranties
Warranty period from the shipment date	18 months
Warranty period from the project startup date	12 months
Change in warranty reserve
Beginning Balance	$ 1,252	$ 1,449
Payments and replacement product	(1,495)	(677)
Additions to warranty reserve for warranties issued during the period	1,647	485
Change in the warranty reserve for pre-existing warranties	(2)	(5)
Ending Balance	$ 1,402	$ 1,252