Property, Plant and Equipment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Property, Plant and Equipment
Gross property, plant, and equipment	$ 190,147		$ 190,147		$ 191,322
Less accumulated depreciation and amortization, including accumulated amortization of finance leases	110,478		110,478		109,008
Property, plant, and equipment - net (Note 7)	79,669		79,669		82,314
Depreciation	2,613	$ 2,768	5,320	$ 5,540
Asset impairment	3,847		3,847
Land
Property, Plant and Equipment
Gross property, plant, and equipment	11,531		11,531		11,076
Improvements to land and leaseholds
Property, Plant and Equipment
Gross property, plant, and equipment	17,548		17,548		17,172
Buildings
Property, Plant and Equipment
Gross property, plant, and equipment	32,577		32,577		35,241
Machinery and equipment, including equipment under finance leases
Property, Plant and Equipment
Gross property, plant, and equipment	121,251		121,251		122,599
Construction in progress
Property, Plant and Equipment
Gross property, plant, and equipment	$ 7,240		$ 7,240		$ 5,234