Composition of Certain Balance Sheet Items - Schedule of Property and Equipment (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Property Plant And Equipment [Abstract]
Machinery and equipment	$ 5,633	$ 5,449
Leasehold improvements	1,920	1,651
Purchased computer software	85	85
Property and equipment, gross	7,638	7,185
Less: accumulated depreciation and amortization	(3,909)	(3,743)
Property plant and equipment, net	$ 3,729	$ 3,442	[1]

[1] Amounts have been derived from the December 31, 2012 audited consolidated financial statements.