Quarterly report pursuant to Section 13 or 15(d)

Capital Structure - Additional Information (Detail)

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Capital Structure - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended 12 Months Ended 13 Months Ended
Aug. 03, 2018
Jul. 25, 2017
Jul. 27, 2016
Jun. 12, 2015
Aug. 01, 2014
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Jun. 30, 2014
Class of Stock [Line Items]                      
Common stock, shares authorized           200,000,000   200,000,000   200,000,000  
Common stock, par value           $ 0.0001   $ 0.0001   $ 0.0001  
Initial public offering, closing date               Aug. 01, 2014      
Number of warrants or rights outstanding           30,572,324   30,572,324   31,243,026  
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  
2017 Warrants [Member]                      
Class of Stock [Line Items]                      
Number of warrants or rights outstanding           15,996,450   15,996,450   15,996,450  
Private Placement [Member]                      
Class of Stock [Line Items]                      
Number of shares issued       4,728,128              
Net proceeds received       $ 18,300,000              
Warrants to purchase shares of common stock       2,364,066   189,126   189,126      
Warrant exercise price per share       $ 8.00   $ 4.65   $ 4.65      
Private placement, securities description               Each investor received one share of common stock and a warrant to purchase <div style="white-space: nowrap; color: rgb(0, 0, 0); letter-spacing: 0px; top: 0px;;display:inline;">one-half</div> share of common stock at a price of $4.23 per common share purchased.<table border="0" style="width:100%; table-layout:fixed;" cellspacing="0" cellpadding="0"><tr><td></td></tr></table>      
Exercise price per common share       $ 4.23              
Class of warrant purchase percentage           4.00%   4.00%      
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                
Public offering price, per unit $ 2.00                    
Net proceeds received $ 10,400,000 $ 37,100,000 $ 32,000,000                
Warrants to purchase shares of common stock   16,000,000 14,000,000                
Aggregate gross sales proceeds from common stock   $ 40,000,000 $ 35,000,000                
Warrant exercise price per share   $ 1.55 $ 3.00                
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]                      
Warrants to purchase shares of common stock             1,050   3,550    
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            
Number of warrants or rights outstanding         3,321,416         670,702  
Class of warrant or rights, expired           414,790   670,702   2,645,176  
Representative's Warrant [Member]                      
Class of Stock [Line Items]                      
Warrants to purchase shares of common stock           206,410   206,410      
Warrant exercise price per share           $ 7.50   $ 7.50      
Class of warrant purchase percentage           3.00%   3.00%      
Warrant expiration date               Jul. 28, 2019      
Warrant exercisable period               180 days      
Number of warrants or rights outstanding           206,410   206,410   206,410