Business Segment, Geographic and Quarterly Financial Data - Reporting Segment Net Sales and Gross Margin (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from external customers	$ 79,017us-gaap_Revenues	$ 109,338us-gaap_Revenues	$ 97,644us-gaap_Revenues
Cost of sales	(43,889)us-gaap_CostOfRevenue	(62,521)us-gaap_CostOfRevenue	(56,899)us-gaap_CostOfRevenue
Gross margin	35,128us-gaap_GrossProfit	46,817us-gaap_GrossProfit	40,745us-gaap_GrossProfit
Selling, general and administrative	(35,432)	(36,375)	(32,682)
Research and development	(1,459)us-gaap_ResearchAndDevelopmentExpense	(2,442)us-gaap_ResearchAndDevelopmentExpense	(2,863)us-gaap_ResearchAndDevelopmentExpense
Goodwill impairment	(23,400)us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss	0us-gaap_GoodwillImpairmentLoss
Operating (loss) income	(25,163)us-gaap_OperatingIncomeLoss	8,000us-gaap_OperatingIncomeLoss	5,200us-gaap_OperatingIncomeLoss
Air Pollution Control Segment
Revenues from external customers	42,031	72,552	62,441
Cost of sales	(26,586)	(45,138)	(40,146)
Gross margin	15,445	27,414	22,295
Selling, general and administrative	0	0	0
Research and development	0	0	0
Goodwill impairment	(23,400)
Operating (loss) income	(7,955)	27,414	22,295
FUEL CHEM Segment
Revenues from external customers	36,986	36,786	35,203
Cost of sales	(17,303)	(17,383)	(16,753)
Gross margin	19,683	19,403	18,450
Selling, general and administrative	0	0	0
Research and development	0	0	0
Goodwill impairment	0	0
Operating (loss) income	19,683	19,403	18,450
Other
Revenues from external customers	0	0	0
Cost of sales	0	0	0
Gross margin	0	0	0
Selling, general and administrative	(35,432)	(36,375)	(32,682)
Research and development	(1,459)	(2,442)	(2,863)
Goodwill impairment	0
Operating (loss) income	$ (36,891)	$ (38,817)	$ (35,545)

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

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Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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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.

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Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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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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