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Inventory (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Inventory Disclosure [Abstract]
Raw materials	$ 19,723	$ 19,654
Work in process	5,044	6,855
Inventory, net	24,767	26,509
Allowance for inventory obsolescence	258	211	211
Write-offs of obsolete inventory against allowance	$ 0

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Inventory Valuation Reserves, Deductions

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Carrying amount (lower of cost or market) as of the balance sheet date of inventories less all valuation and other allowances. Excludes noncurrent inventory balances (expected to remain on hand past one year or one operating cycle, if longer).

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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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The amount of the valuation account as of the balance sheet date which reduces the carrying amount of inventory to net realizable value; takes into consideration such factors as market value, excessive quantities based on expected sales, technological obsolescence, and shrinkage. May also provide for estimated product returns or price concessions pertaining to product cost.

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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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