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Property, Plant and Equipment - Narrative (Details) - USD ($)
$ in Thousands
1 Months Ended
Apr. 30, 2018
Jun. 30, 2019
Dec. 31, 2018
Property, Plant and Equipment [Line Items]      
Property, plant and equipment   $ 47,476 $ 46,100
Asset retirement obligation $ 1,300    
Machinery and equipment      
Property, Plant and Equipment [Line Items]      
Purchase price 5,600    
Property, plant and equipment $ 6,900 $ 39,851 $ 38,454