Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2014

Accounting Policies [Abstract]

Assets and Liabilities Measured at Fair Value

Assets and Liabilities Measured at Fair Value were as follows:

	June 30, 2014		December 31, 2013
United States Treasury Obligations (Level 1)	$	374,990,428	$	282,986,507
Commodity Futures Contracts (Level 1)	$	21,250,208	$	13,354,799

Fair Value of Derivative Instruments and Effect of Derivative Instruments on Statements of Income and Expenses

The Fair Value of Derivative Instruments is as follows:

Derivatives not Accounted for as Hedging Instruments	Statements of Financial Condition Location	Net Unrealized Appreciation / (Depreciation) at June 30, 2014		Net Unrealized Appreciation / (Depreciation) at December 31, 2013
Commodity Futures Contracts	Net Unrealized Appreciation (Depreciation) on Futures Contracts	$	21,250,208	$	13,354,799

The Effect of Derivative Instruments on the Statements of Income and Expenses is as follows:

		For the Three Months Ended June 30, 2014				For the Three Months Ended June 30, 2013
Derivatives not Accounted for as Hedging Instruments	Location of Gain or (Loss) on Derivatives Recognized in Income	Realized Gain or (Loss) on Derivatives Recognized in Income		Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income		Realized Gain or (Loss) on Derivatives Recognized in Income			Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income
Commodity Futures Contracts	Net Realized Gain (Loss) on Futures	$	5,906,143		—	$	(210,017	)		—
	Net Change in Unrealized Gain (Loss) on Futures		—	$	11,470,118		—		$	(16,179,726	)

		For the Six Months Ended June 30, 2014				For the Six Months Ended June 30, 2013
Derivatives not Accounted for as Hedging Instruments	Location of Gain or (Loss) on Derivatives Recognized in Income	Realized Gain or (Loss) on Derivatives Recognized in Income		Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income		Realized Gain or (Loss) on Derivatives Recognized in Income		Change in Unrealized Gain or (Loss) on Derivatives Recognized in Income
Commodity Futures Contracts	Net Realized Gain (Loss) on Futures	$	10,294,633		—	$	311,881		—
	Net Change in Unrealized Gain (Loss) on Futures		—	$	7,895,409		—	$	(9,747,415	)

Summary of Gross and Net Amounts of Offsetting Assets

 The following table presents the gross and net amounts of these assets and liabilities with any offsets to reflect the Fund’s ability to enforce the master netting agreements at June 30, 2014:

								Gross Amounts Not Offset in the Statement of Financial Condition
Assets	Gross Amount of Recognized Assets		Gross Amounts Offset in the Statement of Financial Condition			Net Amounts of Assets Presented in the Statement of Financial Condition		Financial Instruments		Cash Collateral Pledged		Net Amount
Commodity Futures Contracts	$	21,389,878	$	(139,670	)	$	21,250,208	$	—	$	—	$	21,250,208

The following table presents the gross and net amounts of these assets and liabilities with any offsets to reflect the Fund’s ability to enforce the master netting agreements at December 31, 2013:

								Gross Amounts Not Offset in the Statement of Financial Condition
Assets	Gross Amount of Recognized Assets		Gross Amounts Offset in the Statement of Financial Condition			Net Amounts of Assets Presented in the Statement of Financial Condition		Financial Instruments		Cash Collateral Pledged		Net Amount
Commodity Futures Contracts	$	13,418,884	$	(64,085	)	$	13,354,799	$	—	$	—	$	13,354,799