Share-Based Compensation Expense - Estimated Share-based Compensation Expense Related to Equity Awards Granted to Employees and Non-employee Directors (Detail) (USD $)
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3 Months Ended | |
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Mar. 31, 2014
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Mar. 31, 2013
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||
Share-based compensation expense | $ 399,454 | $ 351,556 |
Selling, General and Administrative Expense [Member]
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||
Share-based compensation expense | 340,498 | 314,428 |
Research and Development Expense [Member]
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||
Share-based compensation expense | $ 58,956 | $ 37,128 |