Inventories - Inventories (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 30, 2017
Inventory Disclosure [Abstract]
Raw materials	$ 32,811	$ 30,139
Work-in-progress	2,515	2,506
Finished goods		5,171
Inventories	$ 35,326	$ 37,816

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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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