Inventories (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Inventory Disclosure [Abstract]
Raw materials and supplies	$ 80,985		$ 65,221
Work in process	11,815		62,584
Finished goods	2,444		10,665
Inventory, gross	95,244		138,470
Less progress payments	0		16,309
Total	$ 95,244	$ 83,159	$ 122,161

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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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Gross amount, as of the balance sheet date, of merchandise, goods, commodities, or supplies held for future sale or to be used in manufacturing, servicing or production process.

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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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Gross amount of unprocessed materials to be used in manufacturing or production process and supplies that will be consumed.

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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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Amount of advances received from customers under long-term contracts which have been offset against inventories accounts at the balance sheet date.

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