Preferred Stock, Common Stock and Stockholders' Equity - Summary of Recognized Non-Cash Stock-Based Compensation Expense (Detail) - USD ($) |
12 Months Ended | |
|---|---|---|
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||
| Stock-based compensation expense | $ 1,504,356 | $ 1,102,087 |
| Research and development [Member] | ||
| Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||
| Stock-based compensation expense | 579,078 | 410,150 |
| General and administrative [Member] | ||
| Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||
| Stock-based compensation expense | $ 925,278 | $ 691,937 |