Summary of Significant Accounting Policies - Product Warranty Liability (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Balance, beginning of period	$ 73	$ 97
Charged to cost of sales	(1)	90
Actual product warranty expenditures	(45)	(114)
Balance, end of period	$ 27	$ 73