Quarterly report pursuant to Section 13 or 15(d)

Revolving credit line - Narrative (Details)

v3.8.0.1
Revolving credit line - Narrative (Details) - Line of Credit - Revolving Credit Facility - USD ($)
Apr. 30, 2018
Apr. 18, 2018
Mar. 31, 2018
Dec. 31, 2017
Debt Instrument [Line Items]        
Balance of revolving line of credit     $ 4,900,000 $ 4,900,000
Bridge Bank – Revolving Credit Line - March 1, 2012 | Bridge Bank, N.A.        
Debt Instrument [Line Items]        
Remaining borrowing capacity     $ 1,200,000  
Subsequent Event | Bridge Bank – Revolving Credit Line - March 1, 2012 | Bridge Bank, N.A.        
Debt Instrument [Line Items]        
Line of credit facility, maximum borrowing capacity   $ 10,000,000    
Debt instrument, allowable borrowings, percentage of eligible accounts receivable (as percent)   85.00%    
Period for eligible accounts receivable   90 days    
Subsequent Event | Tenth Business Financing Modification Agreement With Western Alliance Bank        
Debt Instrument [Line Items]        
Percentage change in finance charge for outstanding advances (as percent) 0.01%