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Summary of Significant Accounting Policies (Additional Information) (Details)
 12 Months Ended
Dec. 31, 2015
$ / Units
Significant Accounting Policies [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
Creation Baskets  
Significant Accounting Policies [Line Items]  
Number of Shares per basket 50,000
Prior to July 1, 2011  
Significant Accounting Policies [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 1,000
Maximum  
Significant Accounting Policies [Line Items]  
Cash equivalents maturity period 6 months