Property, Plant, and Equipment - Schedule of Property, Plant, and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 5,697	$ 5,510
Less accumulated depreciation	(3,789)	(3,656)
Total property, plant and equipment, net of depreciation	1,908	1,854
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	70	70
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	2,172	1,995
Patterns and tooling [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,574	1,617
Office Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	424	424
IT Equipment and Software [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	1,335	1,282
Field Service Spare Parts [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 122	$ 122