Business Segment and Geographic Disclosures (Detail) - Reporting Segment Net Sales and Gross Margin (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues from external customers	$ 29,092	$ 20,911	$ 51,576	$ 46,123
Cost of sales	(17,227)	(11,880)	(30,279)	(25,100)
Gross margin	11,865	9,031	21,297	21,023
Selling, general and administrative	(9,307)	(7,874)	(17,765)	(16,868)
Research and development	(430)	(969)	(1,363)	(1,475)
Operating income	2,128	188	2,169	2,680
Air Pollution Control Segment [Member]
Revenues from external customers	20,239	12,818	33,186	28,532
Cost of sales	(13,083)	(7,951)	(21,666)	(16,702)
Gross margin	7,156	4,867	11,520	11,830
Selling, general and administrative	0	0	0	0
Research and development	0	0	0	0
Operating income	7,156	4,867	11,520	11,830
Fuel Chem Segment [Member]
Revenues from external customers	8,853	8,093	18,390	17,591
Cost of sales	(4,144)	(3,929)	(8,613)	(8,398)
Gross margin	4,709	4,164	9,777	9,193
Selling, general and administrative	0	0	0	0
Research and development	0	0	0	0
Operating income	4,709	4,164	9,777	9,193
Other Segments [Member]
Revenues from external customers	0	0	0	0
Cost of sales	0	0	0	0
Gross margin	0	0	0	0
Selling, general and administrative	(9,307)	(7,874)	(17,765)	(16,868)
Research and development	(430)	(969)	(1,363)	(1,475)
Operating income	$ (9,737)	$ (8,843)	$ (19,128)	$ (18,343)

The aggregate cost of goods produced and sold and services rendered during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

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Aggregate revenue less cost of goods and services sold or operating expenses directly attributable to the revenue generation activity.

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The net result for the period of deducting operating expenses from operating revenues.

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No definition available.

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The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

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Aggregate revenue recognized during the period (derived from goods sold, services rendered, insurance premiums, or other activities that constitute an entity's earning process). For financial services companies, also includes investment and interest income, and sales and trading gains.

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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