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Commitments and Contingencies - Consulting Agreement - Additional Information (Detail) - Consulting Agreement [Member] - USD ($)
1 Months Ended 3 Months Ended 9 Months Ended 12 Months Ended
Jan. 31, 2014
Sep. 30, 2017
Sep. 30, 2017
Dec. 31, 2016
Commitments And Contingencies [Line Items]        
Milestone payments   $ 0 $ 0 $ 0
Research and development expense related to milestone expense   $ 0 $ 0 $ 0
Clinical Development and Regulatory Milestones [Member]        
Commitments And Contingencies [Line Items]        
Shares of common stock for attaining milestones 126,984      
Milestone payments $ 500,000      
Milestone based issuance of shares 39,681      
Clinical Development and Regulatory Milestones [Member] | Maximum [Member]        
Commitments And Contingencies [Line Items]        
Expected milestone payments $ 2,000,000