Inventories - Schedule of Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
Finished goods	$ 10,467	$ 8,505
Work-in-process	7,846	16,522
Raw materials and purchased parts	121,883	117,789
Stores and supplies	31,391	30,197
Total inventories	$ 171,587	$ 173,013

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of merchandise or goods held by the company that are readily available for sale.

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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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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of items purchased for use as components of a finished product or pieces of machinery and equipment plus any items in their natural and unrefined state. This element may be used when the reporting entity combines raw materials and purchased parts into an aggregate amount.

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Carrying amount, net of valuation reserves and adjustments, as of the balance sheet date of products used directly or indirectly in the manufacturing or production process, which may or may not become part of the final product. May also include items used in the storage, presentation or transportation of physical goods.

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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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