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 | 9 Months Ended | ||
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Sep. 30, 2013
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Sep. 30, 2012
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Sep. 30, 2013
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Sep. 30, 2012
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Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items] | ||||
Share-based compensation expense | $ 442,328 | $ 359,543 | $ 1,159,021 | $ 1,073,872 |
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 | 395,316 | 338,447 | 1,033,921 | 1,036,373 |
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 | $ 47,012 | $ 21,096 | $ 125,100 | $ 37,499 |