Inventories - Schedule of Inventory (Details) - USD ($) $ in Thousands	Jun. 28, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 15,409	$ 15,939
Contracts and other work in process (including certain general stock materials)	124,049	96,667
Finished goods	23,548	18,963
Inventories(1)	$ 163,006	$ 131,569

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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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