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Inventory (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Inventory Disclosure [Abstract]
Allowance for inventory obsolescence	$ 225,000us-gaap_InventoryValuationReserves		$ 225,000us-gaap_InventoryValuationReserves
Raw materials	21,596,000us-gaap_InventoryRawMaterialsNetOfReserves		25,984,000us-gaap_InventoryRawMaterialsNetOfReserves
Work in process	5,882,000us-gaap_InventoryWorkInProcessNetOfReserves		6,640,000us-gaap_InventoryWorkInProcessNetOfReserves
Inventory, net	27,478,000us-gaap_InventoryNet		32,624,000us-gaap_InventoryNet
Write-offs of obsolete inventory against allowance	$ 0ngs_InventoryValuationReservesDeductions	$ 0ngs_InventoryValuationReservesDeductions

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- Definition

Inventory Valuation Reserves, Deductions

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No definition available.

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- Definition

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.6(a))

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of unprocessed items to be consumed in the manufacturing or production process.

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Amount of valuation reserve for inventory.

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Carrying amount, net of reserves and adjustments, as of the balance sheet date of merchandise or goods which are partially completed. This inventory is generally comprised of raw materials, labor and factory overhead costs, which require further materials, labor and overhead to be converted into finished goods, and which generally require the use of estimates to determine percentage complete and pricing.

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