Quarterly report pursuant to Section 13 or 15(d)

Balance Sheet Components - Additional Information (Details)

v3.8.0.1
Balance Sheet Components - Additional Information (Details)
 3 Months Ended 12 Months Ended
Mar. 31, 2018
USD ($)
Customer
Mar. 31, 2017
USD ($)
Customer
Dec. 31, 2017
USD ($)
Customer
Schedule Of Balance Sheet Components [Line Items]      
Unbilled Receivables $ 1,299,000   $ 1,470,000
Accounts receivable, net $ 35,089,000   31,444,000
Percentage of Non-US revenue invoiced in Euros 76.90% 72.20%  
Noncurrent inventories expected to be realized or consumed $ 452,000   644,000
Salvage value of expenditures for additions, improvements and replacements 0    
Repairs and maintenance expense 560,000 $ 651,000  
Depreciation and amortization 2,695,000 3,177,000  
Impairments of long-lived assets 0 0  
Impairment of finite lived intangible assets 0 0  
Amortization of intangible assets 298,000 27,000  
Construction in Process and Computer Software or Development Cost      
Schedule Of Balance Sheet Components [Line Items]      
Depreciation and amortization 0 $ 0  
Customer Concentration Risk | Customer One      
Schedule Of Balance Sheet Components [Line Items]      
Accounts receivable, net 9,461,000   10,394,000
Customer Concentration Risk | Customer Two      
Schedule Of Balance Sheet Components [Line Items]      
Accounts receivable, net $ 8,077,000   $ 6,459,000
Sales Revenue, Net | Customer Concentration Risk      
Schedule Of Balance Sheet Components [Line Items]      
Number of customers | Customer 1 1  
Net Accounts Receivable | Customer Concentration Risk      
Schedule Of Balance Sheet Components [Line Items]      
Number of customers | Customer 2   2
Raw materials | Supplier Concentration Risk | Vendor one      
Schedule Of Balance Sheet Components [Line Items]      
Concentration risk, percentage 18.50% 18.80%  
Raw materials | Supplier Concentration Risk | Vendor two      
Schedule Of Balance Sheet Components [Line Items]      
Concentration risk, percentage 15.10% 11.60%  
Raw materials | Supplier Concentration Risk | Vendor three      
Schedule Of Balance Sheet Components [Line Items]      
Concentration risk, percentage 12.00% 10.90%