Inventories - Summary of inventories (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Inventory Disclosure [Abstract]
Raw materials and common parts, net of reserve	$ 6,939	$ 6,832
Work-in-process	2,902	2,380
Finished goods, net of reserve	2,663	2,717
Total inventories	$ 12,504	$ 11,929

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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 raw materials 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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