Quarterly report pursuant to Section 13 or 15(d)

Balance Sheet Components - Schedule of Net Accounts Receivable Balance Concentrations by Major Category (Parenthetical) (Details)

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Balance Sheet Components - Schedule of Net Accounts Receivable Balance Concentrations by Major Category (Parenthetical) (Details)
9 Months Ended 12 Months Ended
Sep. 30, 2018
USD ($)
Customer
Dec. 31, 2017
USD ($)
Customer
Accounts Notes And Loans Receivable [Line Items]    
Accounts receivable, gross $ 37,657,000 $ 34,710,000
Customer Concentration Risk | Business To Business Receivables    
Accounts Notes And Loans Receivable [Line Items]    
Number of customers | Customer 1 1
Accounts receivable, gross $ 13,207,000 $ 10,394,000
Credit insurance policy, deductible amount $ 400,000  
Credit insurance policy, retention percentage 10.00%  
Customer Concentration Risk | Business To Business Receivables | Maximum    
Accounts Notes And Loans Receivable [Line Items]    
Credit insurance policy, coverage limit $ 18,000,000 $ 12,000,000