Basis of Presentation and Significant Accounting Policies - Stock-Based Compensation Expense (Detail) (USD $)
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3 Months Ended | 9 Months Ended | ||
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Sep. 30, 2014
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Sep. 30, 2013
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Sep. 30, 2014
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Sep. 30, 2013
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||||
Total stock-based compensation | $ 444,626 | $ 46,665 | $ 490,326 | $ 133,305 |
Research and Development [Member]
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||||
Total stock-based compensation | 35,704 | 23,133 | 59,583 | 63,508 |
General and Administrative [Member]
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||||
Total stock-based compensation | $ 408,922 | $ 23,532 | $ 430,743 | $ 69,797 |