Property, Plant and Equipment (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) a	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) a	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Property, Plant and Equipment
Property, plant and equipment - gross	$ 188,272,000		$ 188,272,000		$ 189,076,000
Less accumulated depreciation and amortization, including accumulated amortization of capitalized leases	(100,378,000)		(100,378,000)		(92,980,000)
Total property, plant and equipment, net	87,894,000		87,894,000		96,096,000
Depreciation	2,803,000	$ 3,178,000	8,685,000	$ 9,705,000
Asset impairment charge			0	0
Proceeds from the sale of property, plant, and equipment			2,267,000	$ 1,388,000
Land
Property, Plant and Equipment
Property, plant and equipment - gross	$ 12,535,000		$ 12,535,000		14,869,000
Area of land (in acres) | a	54.5		54.5
Proceeds from the sale of property, plant, and equipment			$ 2,047,000
Loss on sale			269,000
Improvements to land and leaseholds
Property, Plant and Equipment
Property, plant and equipment - gross	$ 17,482,000		17,482,000		17,415,000
Buildings
Property, Plant and Equipment
Property, plant and equipment - gross	34,860,000		34,860,000		34,929,000
Machinery and equipment, including equipment under capitalized leases
Property, Plant and Equipment
Property, plant and equipment - gross	120,671,000		120,671,000		120,806,000
Construction in progress
Property, Plant and Equipment
Property, plant and equipment - gross	$ 2,724,000		$ 2,724,000		$ 1,057,000