Segment Reporting (Detail) - Company`s reportable segments (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net sales
Net sales	$ 13,307	$ 16,999
(Loss) income from operations
Income (loss) from operations	(1,994)	(2,425)
Heavy Duty Diesel Systems [Member]
Net sales
Net sales	7,284	12,601
(Loss) income from operations
Income (loss) from operations	(337)	(364)
Catalyst [Member]
Net sales
Net sales	6,456	6,104
(Loss) income from operations
Income (loss) from operations	121	(332)
Corporate [Member]
(Loss) income from operations
Income (loss) from operations	(1,817)	(1,688)
Eliminations [Member]
Net sales
Net sales	(433)	(1,706)
(Loss) income from operations
Income (loss) from operations	$ 39	$ (41)