Summary of Significant Accounting Policies - Additional Information (Details)
3 Months Ended 12 Months Ended
Apr. 20, 2018
Mar. 31, 2018
USD ($)
Mar. 31, 2017
USD ($)
Dec. 31, 2017
USD ($)
Summary Of Significant Accounting Policies [Line Items]        
Accumulated deficit   $ (103,013,000)   $ (86,880,000)
Net losses   (16,133,000) $ (8,934,000)  
Net cash used in operating activities   (11,883,000) $ (7,860,000)  
Deferred offering costs   $ 1,707,000   $ 0
Off-balance sheet concentrations of credit risk description   As of March 31, 2018, the Company had no off-balance sheet concentrations of credit risk.    
Off-balance sheet concentrations of credit risk   $ 0    
Federal statutory income tax rate   21.00%   35.00%
Limitation of net operating loss deduction as percentage of current year taxable income   80.00%    
Subsequent Event        
Summary Of Significant Accounting Policies [Line Items]        
Reverse split of shares of common and convertible preferred stock, conversion ratio 0.33898      
Reverse split of shares of common and convertible preferred stock, effective date Apr. 20, 2018      
Amended and Restated Certificate of Incorporation | Subsequent Event        
Summary Of Significant Accounting Policies [Line Items]        
Reverse split of shares of common and convertible preferred stock 1-for-2.95 reverse split