Property, Plant and Equipment - Summary of property, plant and equipment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 24,284	$ 21,130
Less accumulated depreciation and amortization	(14,909)	(14,270)
Total property, plant and equipment	9,375	6,860
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	7,916	7,851
Machinery, equipment and tooling
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	13,530	12,781
Construction in progress
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 2,817	$ 477