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Organization and Business - Additional Information (Detail) (USD $)
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1 Months Ended | 30 Months Ended | 1 Months Ended | ||||||
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Feb. 26, 2008
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Nov. 30, 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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Feb. 29, 2012
Creation Baskets
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Feb. 29, 2012
Prior to February 29, 2012
Creation Baskets
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Jun. 30, 2011
Prior to July 1, 2011
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| Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items] | |||||||||
| Number of units per basket | $ 50,000 | $ 100,000 | |||||||
| Number of initially registered units on Form S-1 with the U.S. Securities and Exchange Commission | 30,000,000 | ||||||||
| Net asset value per unit | $ 50.00 | $ 59.89 | $ 58.39 | $ 48.37 | $ 42.06 | ||||
| Number of units issued | 300,000 | ||||||||
| Value of units issued | $ 15,000,000 | ||||||||
| Number of registered units | 72,800,000 | ||||||||
| 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 | |||||||