Quarterly report pursuant to Section 13 or 15(d)

Subsequent Events - Additional Information (Detail)

v3.19.3
Subsequent Events - Additional Information (Detail) - USD ($)
Nov. 05, 2019
Oct. 29, 2019
Oct. 28, 2019
Sep. 30, 2019
Dec. 31, 2018
Subsequent Event [Line Items]          
Preferred stock, shares issued       0 0
Preferred stock, par value       $ 0.001 $ 0.001
Subsequent Event | Loan Agreement | Pacific Mercantile Bank          
Subsequent Event [Line Items]          
Line of credit facility, maximum borrowing capacity     $ 3,000,000    
Maximum borrowing base percentage of eligible accounts     90.00%    
Maximum borrowing base percentage of eligible inventory     75.00%    
Line of credit facility expiration date     Oct. 28, 2021    
Interest rate     1.50%    
Subsequent Event | Loan Agreement | Exim Bank          
Subsequent Event [Line Items]          
Line of credit facility expiration date     Oct. 28, 2020    
Initial and annual fee     $ 52,500    
Termination fee     $ 30,000    
Maximum | Subsequent Event | Loan Agreement | Pacific Mercantile Bank          
Subsequent Event [Line Items]          
Interest rate     6.00%    
Series E Participating Convertible Preferred Stock | Subsequent Event          
Subsequent Event [Line Items]          
Convertible preferred stock, shares issued upon conversion   100      
Convertible preferred stock, conversion price per share   $ 0.5750      
Underwritten Public Offering | Subsequent Event          
Subsequent Event [Line Items]          
Net proceeds from issuance of common stock   $ 4,200,000      
Underwritten Public Offering | Common Stock | Subsequent Event          
Subsequent Event [Line Items]          
Shares issued   7,820,000      
Shares issued, price per share   $ 0.5750      
Over-Allotment Option | Subsequent Event          
Subsequent Event [Line Items]          
Shares issued 1,100,000        
Gross proceeds from issuance of equity $ 600,000        
Over-Allotment Option | Maximum | Subsequent Event          
Subsequent Event [Line Items]          
Option to purchase additional common stock granted   1,173,000      
Private Placement | Series E Participating Convertible Preferred Stock | Subsequent Event          
Subsequent Event [Line Items]          
Shares issued, price per share   $ 57.50      
Preferred stock, shares issued   69,565      
Preferred stock, par value   $ 0.001      
Gross proceeds from issuance of convertible preferred stock   $ 4,000,000