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Organization and Business (Additional Information) (Details) (USD $)
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1 Months Ended | |||||||||||||||||
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Dec. 06, 2007
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Dec. 04, 2007
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2009
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Feb. 29, 2012
Creation Baskets
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Feb. 29, 2012
Redemption Baskets [Member]
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Dec. 31, 2013
Beginning on January 1, 2013 and after
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Dec. 31, 2013
Open Cleared Swap and Futures Contracts
Open Futures Contracts, Long
United States
Contracts
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Dec. 31, 2012
Open Cleared Swap and Futures Contracts
Open Futures Contracts, Long
United States
Contracts
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| Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] | ||||||||||||||||||
| Number of Contracts | 649 | [1] | 1,068 | [2] | ||||||||||||||
| Number of shares per basket | 50,000 | 100,000 | ||||||||||||||||
| Fee paid by Authorized Purchasers for each order placed to create one or more Creation Baskets or to redeem one or more baskets | $ 350 | $ 1,000 | ||||||||||||||||
| Number of initially registered units on Form S-1 with the U.S. Securities and Exchange Commission | 11,000,000 | |||||||||||||||||
| Net asset value per share | $ 50.00 | $ 42.83 | $ 39.81 | $ 43.46 | $ 42.91 | $ 42.91 | ||||||||||||
| Number of shares issued | 300,000 | |||||||||||||||||
| Value of shares issued | $ 15,000,000 | |||||||||||||||||
| Commenced investment operations date | Dec. 06, 2007 | |||||||||||||||||
| Number of registered shares | 111,000,000 | |||||||||||||||||
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