Balance Sheet Components - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Depreciation of property and equipment	$ 843,000	$ 647,000	$ 206,000
Removal of fully depreciated property, machinery and equipment	$ 150,000	$ 72,000	$ 40,000