Inventories - Summary of inventories (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Inventory Disclosure [Abstract]
Raw materials and common parts	$ 6,160	$ 6,189
Work-in-process	3,258	2,460
Finished goods	2,515	2,564
Total inventories, net of reserve	$ 11,933	$ 11,213

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Amount before valuation and LIFO reserves of completed merchandise or goods expected to be sold within one year or operating cycle, if longer.

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

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Amount before valuation and LIFO reserves of merchandise or goods in the production process expected to be completed within one year or operating cycle, if longer.

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