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Financial Instruments, Off-Balance Sheet Risks and Contingencies - Additional Information (Detail) (USD $)
Dec. 31, 2012
Dec. 31, 2011
Carrying Amounts and Fair Values of Financial Instruments or Liabilities [Line Items]    
Cash investments in money market funds $ 86,156,064 $ 107,128,288
Deposits in domestic and foreign financial institutions $ 12,085,820 $ 58,744,673