Segment Reporting - Net Sales (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Net sales
Net sales	$ 39,738	$ 41,231
Catalyst
Net sales
Net sales	26,224	23,772
Heavy Duty Diesel Systems
Net sales
Net sales	16,664	19,577
Intersegment Eliminations
Net sales
Net sales	$ (3,150)	$ (2,118)