Lease Commitment and Total Rental Expense - Additional Information (Detail) (USD $)
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12 Months Ended | ||
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Schedule of Rent Expense [Line Items] | |||
Rental expenses | $ 177,416 | $ 145,207 | $ 191,717 |