Inventories (Details) - USD ($)	Dec. 31, 2019	Dec. 31, 2018
Inventories
Raw materials, parts and supplies of inventories	$ 100,947,000	$ 130,083,000
Reserve for obsolete and slow moving inventory	$ 10,467,000	$ 10,168,000

Amount of valuation reserve for inventory.

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-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant