Segment Reporting (Detail) - Companys reportable segments (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues	$ 14,400	$ 14,974	$ 48,123	$ 40,290
Income (loss) from operations	(1,156)	(1,250)	(5,460)	(6,669)
Heavy Duty Diesel Systems [Member]
Revenues	8,680	11,076	32,283	30,105
Income (loss) from operations	(272)	373	(545)	84
Catalyst [Member]
Revenues	6,659	6,447	19,194	15,002
Income (loss) from operations	261	(170)	(750)	(1,064)
Corporate [Member]
Revenues
Income (loss) from operations	(1,209)	(1,381)	(4,251)	(5,509)
Intersegment Elimination [Member]
Revenues	(939)	(2,549)	(3,354)	(4,817)
Income (loss) from operations	$ 64	$ (72)	$ 86	$ (180)