Property, Plant and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, plant and equipment
Property, plant, and equipment, gross	$ 35,225	$ 31,851
Less: accumulated depreciation	(27,970)	(26,539)
Property, plant, and equipment, net	7,255	5,312
Property, plant and equipment consist of the following
Depreciation expense	(1,500)	(1,400)	$ (1,400)
Land.
Property, plant and equipment
Property, plant, and equipment, gross	90	90
Buildings.
Property, plant and equipment
Property, plant, and equipment, gross	15,332	15,332
Building improvements
Property, plant and equipment
Property, plant, and equipment, gross	5,169	5,032
Software, machinery and equipment
Property, plant and equipment
Property, plant, and equipment, gross	$ 14,634	$ 11,397