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Fair Value of Financial Instruments (Effect of Derivative Instruments on Condensed Statements of Operations) (Details) (USD $)
3 Months Ended 9 Months Ended
Sep. 30, 2014
Sep. 30, 2013
Sep. 30, 2014
Sep. 30, 2013
Derivative Instruments, Gain (Loss) [Line Items]        
Realized Gain on Derivatives Recognized in Income $ 454,600 $ 2,762,210 $ 2,495,090 $ 5,060,870
Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income     (3,251,600) 2,012,810
Commodity Contracts | Futures | Realized gain on closed positions
       
Derivative Instruments, Gain (Loss) [Line Items]        
Realized Gain on Derivatives Recognized in Income     2,495,090 5,060,870
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     $ (3,251,600) $ 2,012,810