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 |