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Summary of Significant Accounting Policies (Additional Information) (Detail)
 3 Months Ended
Mar. 31, 2015
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 1,000uso_FeePaidPerOrder
Maximum [Member]  
Significant Accounting Policies [Line Items]  
Minimum likelihood of tax benefits being recognized upon ultimate settlement 50.00%uso_PercentageOfIncomeTaxExaminationMinimumLikelihoodOfTaxBenefitsBeingRealizedUponSettlement
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
Cash equivalents maturity period 6 months
Creations and Redemptions Basket [Member]  
Significant Accounting Policies [Line Items]  
Number of units per basket 100,000uso_NumberOfUnitPerBasket
/ invest_InvestmentSecuritiesClassAxis
= uso_RedemptionBasketsMember