Other Accrued Expenses and Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accrued Liabilities And Other Liabilities Current [Abstract]
Accrued professional fees	$ 1,205	$ 1,065
Accrued warranties	319	75
Income taxes payable	47	19
Other accrued expenses	1,426	861
Total	$ 2,997	$ 2,020