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Fair Value of Financial Instruments (Effect of Derivative Instruments on Condensed Statements of Operations) (Details) (USD $)
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]      
Realized Gain or (Loss) on Derivatives Recognized in Income $ 6,302,760 $ (6,954,520) $ 16,224,040
Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income 85,540 (2,445,210) (11,864,440)
Commodity Contracts | Futures | Realized gain on closed positions
     
Derivative Instruments, Gain (Loss) [Line Items]      
Realized Gain or (Loss) on Derivatives Recognized in Income 6,302,760 (6,954,520) 16,224,040
Commodity Contracts | Futures | Change in unrealized gain (loss) on open positions
     
Derivative Instruments, Gain (Loss) [Line Items]      
Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income $ 85,540 $ (2,445,210) $ (11,864,440)