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Stockholders' Equity - Summary of Number of Shares of Common Stock Reserved (Detail) - shares
Dec. 31, 2015
Dec. 31, 2014
Class Of Stock [Line Items]    
Reserved shares of common stock 4,296,440 3,689,767
Common stock options [Member]    
Class Of Stock [Line Items]    
Reserved shares of common stock 3,995,876 3,561,104
Warrants to Purchase Common Stock [Member]    
Class Of Stock [Line Items]    
Reserved shares of common stock 300,564 128,663