Quarterly report pursuant to Section 13 or 15(d)

Warrants - Additional Information (Detail)

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Warrants - Additional Information (Detail) - USD ($)
6 Months Ended
Jun. 30, 2015
Jun. 30, 2013
Class of Warrant or Right [Line Items]    
Issuance of common stock shares 8,896,848 301,778
Weighted average exercise price of warrants $ 0.99  
Weighted average remaining life of warrants 4 years  
Number of shares purchased for warrants exercised 4,598,129  
Net proceeds from warrants exercised $ 4,398,000  
Number of warrants issued 0  
Number of warrants cancelled 0  
Warrant Agreement [Member]    
Class of Warrant or Right [Line Items]    
Issuance of common stock shares 176,145  
Number of shares purchased for warrants exercised 215,000