Goodwill and Other Intangibles (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended				9 Months Ended		0 Months Ended
	Sep. 30, 2014 reporting_unit	Dec. 31, 2013	Sep. 30, 2014 Fuel Chem Technology Segment [Member]	Dec. 31, 2013 Fuel Chem Technology Segment [Member]	Sep. 30, 2014 APC Technology Segment [Member]	Dec. 31, 2013 APC Technology Segment [Member]	Sep. 18, 2014 Intellectual Property [Member]	Sep. 30, 2014 PECO and FGC Acquisitions [Member]	Apr. 30, 2014 PECO and FGC Acquisitions [Member] Other Intangible Assets [Member]
Number of reporting units	2
Goodwill	$ 26,139	$ 21,051	$ 1,723	$ 1,723	$ 24,416	$ 19,328		$ 5,088
Goodwill, Period Increase					5,088
Other intangible assets, net	10,616	4,305
Identifiable intangible assets								4,126	4,126
Finite-lived intangible assets acquired							$ 3,010