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Stock-Based Compensation - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended 9 Months Ended
Apr. 30, 2018
Sep. 30, 2018
Sep. 30, 2017
Sep. 30, 2018
Sep. 30, 2017
Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Aggregate number of common stock   3,348,632   3,348,632   1,912,980
Number of awards granted       1,612,700    
Unrecognized compensation cost related to stock options   $ 4,568,480   $ 4,568,480    
Weighted-average fair value of options granted   $ 2.13   $ 2.24    
Stock Option [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Vesting period       48 months    
Compensation expense for stock options   $ 759,978 $ 53,814 $ 2,314,201 $ 173,888  
Weighted average period expected to be recognized       2 years 7 months 17 days    
Restricted Stock [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Compensation expense for stock options   $ 46,433 $ 73,545 $ 449,689 $ 220,380  
2011 Equity Incentive Plan [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Aggregate number of common stock   821,914   821,914   898,962
2017 Stock Option and Incentive Plan [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Common stock shares available for issuance 1,082,802 4,600,000   4,600,000    
Percentage applied to the outstanding shares as annual increase in number of shares authorized for issuance 4.00%     4.00%    
2017 Stock Option and Incentive Plan [Member] | Stock Option [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Common stock shares available for issuance   2,962,062   2,962,062   3,391,960
Term of options to be granted       10 years    
Number of awards granted   97,500 0 1,612,700 0  
2017 Stock Option and Incentive Plan [Member] | Stock Option [Member] | One-year Anniversary [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Vesting percentage       25.00%    
Two Thousand Seventeen And Two Thousand Eleven Plan            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Aggregate number of common stock   2,615,062   2,615,062   1,179,410
Two Thousand Seventeen And Two Thousand Eleven Plan | Inducement Stock Awards [Member]            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Aggregate number of common stock   733,570   733,570   733,570