Annual report pursuant to Section 13 and 15(d)

Common Stock - Summary of Outstanding Warrants (Parenthetical) (Detail)

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Common Stock - Summary of Outstanding Warrants (Parenthetical) (Detail)
 12 Months Ended
Dec. 31, 2017
Series A Warrants [Member]  
Class of Warrant or Right [Line Items]  
Warrants issued date 2014-07
Series B Warrants [Member]  
Class of Warrant or Right [Line Items]  
Warrants issued date 2014-07
Series A-1 Warrants [Member]  
Class of Warrant or Right [Line Items]  
Warrants issued date 2015-04
Warrants Issued In September 2017 [Member]  
Class of Warrant or Right [Line Items]  
Warrants issued date 2017-09