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Balance Sheet Components - Additional Information (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Property Plant And Equipment [Abstract]        
Depreciation and amortization expense $ 500 $ 200 $ 1,103 $ 646