Property, Plant and Equipment - Summary of property, plant and equipment (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015		Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 24,563		$ 24,284
Less accumulated depreciation and amortization	(15,068)		(14,909)
Total property, plant and equipment	9,495	[1]	9,375
Land
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	21		21
Buildings
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	7,938		7,916
Machinery, equipment and tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	13,776		13,530
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Gross	$ 2,828		$ 2,817

[1] Unaudited