Segment Reporting - Income (Loss) from Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Income (loss) from operations
Income (loss) from operations	$ (10,319)	$ (7,625)
Catalyst
Income (loss) from operations
Income (loss) from operations	(1,612)	(775)
Heavy Duty Diesel Systems
Income (loss) from operations
Income (loss) from operations	(1,699)	183
Corporate, Non-Segment
Income (loss) from operations
Income (loss) from operations	(6,780)	(6,894)
Intersegment Eliminations
Income (loss) from operations
Income (loss) from operations	$ (228)	$ (139)