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The Company and Basis of Presentation - Additional Information (Details)
1 Months Ended 3 Months Ended
Apr. 30, 2018
USD ($)
$ / shares
shares
Mar. 31, 2018
USD ($)
Segment
Dec. 31, 2017
USD ($)
Organization Consolidation And Presentation Of Financial Statements [Line Items]      
Number of operating segments | Segment   1  
Working capital   $ 43,100,000  
Accumulated deficit   (80,632,000) $ (72,513,000)
Cash, cash equivalents and marketable securities   $ 43,500,000  
Subsequent Event | Common Stock      
Organization Consolidation And Presentation Of Financial Statements [Line Items]      
Number of shares issued | shares 5,046,510    
Public offering price | $ / shares $ 8.00    
Proceeds from issuance of common stock upon initial public offering, net $ 37,700,000    
Underwriting discounts and commissions 2,400,000    
Estimated offering costs $ 280,000    
Subsequent Event | Common Stock | Underwriters' Over-allotment Option      
Organization Consolidation And Presentation Of Financial Statements [Line Items]      
Number of shares issued | shares 546,510