Summary of Significant Accounting Policies - Roll Forward of Warranty Cost (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Beginning accrual balance	$ 14	$ 25	$ 36
Warranty provision	54	58	96
Usage	(49)	(69)	(107)
Ending accrual balance	$ 19	$ 14	$ 25