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Organization and Business (Additional Information) (Details) (USD $) | 0 Months Ended |  |  |  |
--- | --- | --- | --- | --- | ---
Dec. 04, 2007 | Dec. 06, 2007 | Jun. 30, 2014 | Dec. 31, 2013 | Jun. 30, 2013 | Dec. 31, 2012
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |
Fee paid by Authorized Purchasers for each order placed to create one or more Creation Baskets or to redeem one or more baskets |  |  | 350 |  |  |  |
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 | $ 47.17 |  | $ 42.83 | $ 40.07 | $ 39.81
Number of shares issued |  | 300,000 |  |  |  |  |
Value of shares issued |  | $ 15,000,000 |  |  |  |  |
Number of registered shares |  |  | 111,000,000 |  |  |  |
Creation Baskets |  |  |  |  |  |  |
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |
Number of shares per basket |  |  | 50,000 |  |  |  |
Open Futures Contracts, Long | United States |  |  |  |  |  |  |
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] |  |  |  |  |  |  |
Number of Contracts |  |  | 583 | [1] |  |  |
[1] | Collateral amounted to $601,117 on open future contracts.

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