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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
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Feb. 29, 2012
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|---|---|
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Creation Baskets
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| Significant Accounting Policies [Line Items] | |
| Number of units per basket | $ 50,000 |
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Redemption Baskets
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|
| Significant Accounting Policies [Line Items] | |
| Number of units per basket | $ 50,000 |
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Prior to February 29, 2012 | Creation Baskets
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|
| Significant Accounting Policies [Line Items] | |
| Number of units per basket | $ 100,000 |
|
Prior to February 29, 2012 | Redemption Baskets
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|
| Significant Accounting Policies [Line Items] | |
| Number of units per basket | $ 100,000 |