Deferred Warranty Revenue and Warranty Reserve - Schedule of Warranty Activity (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Standard Product Warranty Disclosure [Abstract]
Balance, beginning of period	$ 43	$ 85	$ 116
Provision for warranty claims	165	165	173
Product or cash issued to settle claims	(55)	(207)	(204)
Balance, end of period	$ 153	$ 43	$ 85