Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail)

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Summary of Significant Accounting Policies - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Detail) - shares
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Summary Of Significant Accounting Policies [Line Items]    
Potentially dilutive securities 7,420,048 7,359,173
Financing Warrant to Purchase Common Stock [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Potentially dilutive securities 13,889 13,889
IPO Warrants to Purchase Common Stock [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Potentially dilutive securities   11,600
Investor Relations Consulting Warrant [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Potentially dilutive securities   7,950
Investor Relations Incentive Warrant [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Potentially dilutive securities   15,000
Warrant Issued to Private Investors [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Potentially dilutive securities 3,035,688 2,381,675
Employee Stock Option [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Potentially dilutive securities 857,507 1,301,844
Restricted Stock Units (RSUs) [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Potentially dilutive securities 2,641,405 2,473,598
Performance Share Units [Member]    
Summary Of Significant Accounting Policies [Line Items]    
Potentially dilutive securities 871,559 1,153,617