Fair Value Of Financial Instruments (Effect of Derivative Instruments on Condensed Statements of Operations) (Details) (Commodity Contracts [Member], USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Futures - Commodity Contracts [Member] | Realized gain (loss) on closed futures positions [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain or (Loss) on Derivatives Recognized in Income	$ 88,254,202	$ (299,391,078)
Futures - Commodity Contracts [Member] | Change in unrealized gain (loss) on open futures positions [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income	48,310,023	(33,696,980)
Swaps - Commodity Contracts [Member] | Realized loss on closed swap contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain or (Loss) on Derivatives Recognized in Income	22,564,790	(91,376,797)
Swaps - Commodity Contracts [Member] | Change in unrealized gain (loss) on open swap contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income	$ 7,555,254	$ (3,365,324)