Inventories - Schedule of Inventory (Details) - USD ($) $ in Thousands	Apr. 02, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Raw materials	$ 19,363	$ 19,502
Contracts and other work in process (including certain general stock materials)	141,866	129,241
Finished goods	36,074	36,329
Inventories	$ 197,303	$ 185,072

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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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