Amount of revenue earned from products sold or services provided under the terms of a contract, including, but not limited to, government contracts and construction contracts, classified as other.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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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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Aggregate revenue during the period from the sale of goods in the normal course of business, after deducting returns, allowances and discounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(a))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Revenue by Geographical Location (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue, Major Customer [Line Items]
Product revenue	$ 16,240	$ 10,797	$ 9,525	$ 7,006	$ 10,125	$ 10,175	$ 9,251	$ 7,632	$ 43,568	$ 37,183	$ 34,223
Government contract revenue	$ 2,378	$ 2,285	$ 1,667	$ 1,428	$ 1,831	$ 261			7,758	2,092
Total revenue									51,326	39,275	34,223
FRANCE
Revenue, Major Customer [Line Items]
Product revenue									9,692	3,485	7,732
UNITED STATES
Revenue, Major Customer [Line Items]
Product revenue									6,316	4,480	563
Government contract revenue									7,758	2,092
BELGIUM
Revenue, Major Customer [Line Items]
Product revenue									6,263	6,392	5,728
SPAIN
Revenue, Major Customer [Line Items]
Product revenue									3,432	3,360	4,070
KUWAIT
Revenue, Major Customer [Line Items]
Product revenue									2,788	4,415	1,959
Other Countries
Revenue, Major Customer [Line Items]
Product revenue									$ 15,077	$ 15,051	$ 14,171