Property, plant and equipment, net - Components of Property, Plant and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Property Plant And Equipment [Abstract]
Land	$ 260	$ 260
Buildings and improvements	3,893	3,882
Office furniture and equipment	2,438	2,172
Tooling and equipment	5,837	5,505
Transportation equipment	223	223
Construction in progress	3,369	594
Property, plant and equipment, at cost	16,020	12,636
Accumulated depreciation	(6,083)	(5,491)
Property, plant and equipment, net	$ 9,937	$ 7,145