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Stock-Based Compensation - Additional Information (Detail) (USD $)
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9 Months Ended | 12 Months Ended | 9 Months Ended | 9 Months Ended | 9 Months Ended | 9 Months Ended | |||||||||
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Sep. 30, 2013
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Sep. 30, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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Sep. 30, 2013
Nineteen Ninety Four Plan
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Dec. 31, 2004
Nineteen Ninety Four Plan
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Sep. 30, 2013
Nineteen Ninety Four Plan
Maximum
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Sep. 30, 2013
Two Thousand Three Plan
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Sep. 18, 2003
Two Thousand Three Plan
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Sep. 30, 2013
Two Thousand Three Plan
Maximum
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Dec. 31, 2010
Amended Two Thousand Three Plan
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Dec. 31, 2008
Amended Two Thousand Three Plan
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Dec. 31, 2007
Amended Two Thousand Three Plan
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Sep. 30, 2013
Restricted Stock
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Sep. 30, 2013
Employee Restricted Stock Plan
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||||||||||||||
| An aggregate number of common stock authorized | 450,000 | 450,000 | 1,160,000 | 810,000 | 670,000 | 2,000,000 | |||||||||
| Shares of common stock vested and exercisable | 0 | 406,353 | |||||||||||||
| Percentage of option price | 100.00% | 100.00% | |||||||||||||
| Stock option period | 10 years | 10 years | |||||||||||||
| Common stock vesting period | 3 years | 3 years | |||||||||||||
| Shares of common stock unvested | 667 | ||||||||||||||
| Number of options granted | 0 | 54,250 | |||||||||||||
| Weighted average fair value of options granted at market | $ 0.39 | ||||||||||||||
| Number of options exercised | 108,146 | ||||||||||||||
| Intrinsic value of outstanding exercisable options | $ 373 | $ 0 | |||||||||||||
| Common stock reserved for future issuance | 1,041,000 | ||||||||||||||
| Shares available to issued under stock incentive plan | 680,953 | 381,170 | 353,953 | 959,000 | |||||||||||
| Weighted average term | 3 years | ||||||||||||||
| Restricted stock compensation expense | 168,921 | ||||||||||||||
| Unrecognized compensation expense for restricted stock | $ 827,019 | ||||||||||||||
| Weighted average grant date fair value | $ 1.67 | ||||||||||||||