Property, Plant and Equipment (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	$ 188,618,000		$ 188,618,000		$ 185,495,000
Less accumulated depreciation and amortization, including accumulated amortization of capitalized leases	90,082,000		90,082,000		81,522,000
Total property, plant and equipment, net	98,536,000		98,536,000		103,973,000
Asset impairment charge			0
Depreciation	3,178,000	$ 3,295,000	9,705,000	$ 10,620,000
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	14,866,000		14,866,000		14,826,000
Improvements to land and leaseholds
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	17,404,000		17,404,000		17,408,000
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	34,503,000		34,503,000		33,910,000
Machinery and equipment, including equipment under capitalized leases
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	120,414,000		120,414,000		118,060,000
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment - gross	$ 1,431,000		$ 1,431,000		$ 1,291,000