Property, Plant and Equipment (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Land and land improvements	$ 18,194,000	$ 18,374,000
Buildings and structures	36,364,000	36,174,000
Machinery and equipment	193,968,000	176,085,000
Construction in progress	224,000	5,878,000
Property, Plant and Equipment, Gross	248,750,000	236,511,000
Less: accumulated depreciation	(173,465,000)	(170,762,000)
Property, Plant and Equipment, Net	75,285,000	65,749,000
Depreciation	8,200,000	8,100,000	$ 8,200,000
Interest expense capitalized	$ 200,000	$ 100,000	$ 0