Summary of Significant Accounting Policies (Detail 5) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Balance, beginning of period	$ 27	$ 73
Charged to cost of sales	20	(1)
Actual product warranty expenditures	(32)	(45)
Balance, end of period	$ 15	$ 27