Quarterly report pursuant to Section 13 or 15(d)

Capital Structure - Additional Information (Detail)

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Capital Structure - Additional Information (Detail) - USD ($)
1 Months Ended 3 Months Ended 6 Months Ended 9 Months Ended 13 Months Ended
Sep. 30, 2018
Aug. 03, 2018
Jul. 25, 2017
Jul. 27, 2016
Nov. 02, 2015
Jun. 12, 2015
Aug. 01, 2014
Aug. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Sep. 30, 2018
Sep. 30, 2017
Jun. 30, 2014
Dec. 31, 2017
Class of Stock [Line Items]                            
Common stock, shares authorized 200,000,000               200,000,000   200,000,000     200,000,000
Common stock, par value $ 0.0001               $ 0.0001   $ 0.0001     $ 0.0001
Issuance costs allocated to warrants                     $ 0 $ 905,014    
Net proceeds from initial public offering             $ 35,000,000              
Initial public offering, closing date                     Aug. 01, 2014      
Initial public offering, units description                     In August 2014, the Company completed an initial public offering (“IPO”), raising net proceeds of $35.0 million after underwriting discounts, commissions and offering expenses payable by us, through the issuance and sale of our units, which consisted of one share of common stock, one Class A Warrant to purchase one share of common stock at an exercise price of $4.80 per share and one Class B Warrant to purchase one-half share of common stock at an exercise price of $4.00 per full share (“Units”).      
Proceeds from exercise of warrants                     $ 5,503      
Number of warrants or rights outstanding 31,265,182               31,265,182   31,265,182     36,270,103
Common stock, voting rights                     The holders of shares of common stock are entitled to one vote for each share of common stock held at all meetings of stockholders and written actions in lieu of meetings.      
Dividends declared or paid $ 0                          
8.00% Convertible Notes due May 31, 2015 [Member]                            
Class of Stock [Line Items]                            
Convertible Notes, principal amount                         $ 15,000,000  
Convertible Notes, interest rate                         8.00%  
Convertible Notes, due date                         May 31, 2015  
2016 Warrants [Member]                            
Class of Stock [Line Items]                            
Number of warrants or rights outstanding 14,000,000               14,000,000   14,000,000     14,000,000
2017 Warrants [Member]                            
Class of Stock [Line Items]                            
Number of warrants or rights outstanding 15,996,450               15,996,450   15,996,450     16,000,000
Private Placement [Member]                            
Class of Stock [Line Items]                            
Number of shares issued           4,728,128                
Aggregate gross sales proceeds from common stock           $ 20,000,000                
Net proceeds received           $ 18,300,000                
Warrants to purchase shares of common stock 189,126         2,364,066     189,126   189,126      
Warrant exercise price per share $ 4.65         $ 8.00     $ 4.65   $ 4.65      
Warrant expiration term           3 years                
Warrant expiration date                     Jun. 11, 2020      
Initial Public Offering [Member]                            
Class of Stock [Line Items]                            
Conversion of Convertible Notes together with accrued and unpaid interest into common stock, shares             5,109,988              
Follow-on Offering [Member]                            
Class of Stock [Line Items]                            
Number of shares issued   5,750,000 32,000,000 14,000,000                    
Aggregate gross sales proceeds from common stock   $ 11,500,000 $ 40,000,000 $ 35,000,000                    
Net proceeds received   $ 10,400,000 $ 37,100,000 $ 32,000,000                    
Warrants to purchase shares of common stock                 0   3,550      
Follow-on Offering [Member] | CMPO Warrants [Member]                            
Class of Stock [Line Items]                            
Warrants to purchase shares of common stock     16,000,000 14,000,000                    
Follow-on Offering [Member] | 2016 Warrants [Member]                            
Class of Stock [Line Items]                            
Warrant exercise price per share       $ 3.00                    
Warrant expiration term       5 years                    
Fair value of warrants       $ 18,600,000                    
Issuance costs allocated to warrants       $ 1,600,000                    
Follow-on Offering [Member] | 2017 Warrants [Member]                            
Class of Stock [Line Items]                            
Warrant exercise price per share     $ 1.55                      
Warrant expiration term     5 years                      
Fair value of warrants     $ 12,400,000                      
Issuance costs allocated to warrants     $ 900,000                      
Note Warrants [Member]                            
Class of Stock [Line Items]                            
Warrant exercise price per share             $ 3.00              
Warrant expiration term                   5 years        
Number of warrants or rights outstanding 692,858           3,321,416   692,858   692,858     3,315,878
Class of warrant or rights, expired               413,432   2,209,588        
Class B Warrants [Member]                            
Class of Stock [Line Items]                            
Warrant expiration date                     Nov. 02, 2015      
Warrants exercised         4,812,328                  
Common stock shares issued upon exercise of warrants         2,406,164                  
Proceeds from exercise of warrants         $ 9,600,000                  
Class B Warrants [Member] | Initial Public Offering [Member]                            
Class of Stock [Line Items]                            
Warrant exercise price per share             $ 4.00              
Representative's Warrant [Member]                            
Class of Stock [Line Items]                            
Warrants to purchase shares of common stock 206,410               206,410   206,410      
Warrant exercise price per share $ 7.50               $ 7.50   $ 7.50      
Warrant expiration date                     Jul. 28, 2019      
Class of warrant purchase percentage 3.00%               3.00%   3.00%      
Warrant exercisable period                     180 days      
Number of warrants or rights outstanding 206,410               206,410   206,410     206,410
Class A Warrants [Member]                            
Class of Stock [Line Items]                            
Warrant expiration date                     Feb. 01, 2017      
Class A Warrants [Member] | Initial Public Offering [Member]                            
Class of Stock [Line Items]                            
Warrant exercise price per share             $ 4.80