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Summary of Significant Accounting Policies - Additional Information (Detail)
9 Months Ended
Sep. 30, 2015
USD ($)
Segment
Dec. 31, 2014
USD ($)
Summary Of Significant Accounting Policy [Line Items]    
Deferred offering costs   $ 549,000
Number of operating segment | Segment 1  
Leasehold Improvements [Member]    
Summary Of Significant Accounting Policy [Line Items]    
Estimated useful lives of assets 3 years  
Minimum [Member]    
Summary Of Significant Accounting Policy [Line Items]    
Estimated useful lives of assets 3 years  
Maximum [Member]    
Summary Of Significant Accounting Policy [Line Items]    
Estimated useful lives of assets 5 years  
Other Noncurrent Assets [Member]    
Summary Of Significant Accounting Policy [Line Items]    
Long-term portion of restricted cash $ 200,000  
Prepaid Expenses and Other Current Assets [Member]    
Summary Of Significant Accounting Policy [Line Items]    
Current portion of restricted cash $ 25,000