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Organization and Business (Additional Information) (Detail) (USD $)
 0 Months Ended
Apr. 10, 2006
Mar. 31, 2015
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   1,000uso_FeePaidPerOrder
Limited Partners' Capital Account, Units Authorized 17,000,000us-gaap_LimitedPartnersCapitalAccountUnitsAuthorized 1,627,000,000us-gaap_LimitedPartnersCapitalAccountUnitsAuthorized
Limited Partners' Capital Account, Units Issued 200,000us-gaap_LimitedPartnersCapitalAccountUnitsIssued  
Net asset value per unit $ 67.39uso_NetAssetValuePerUnit $ 16.87uso_NetAssetValuePerUnit
Value of units issued $ 13,479,000uso_UnitsIssuedDuringPeriodValueNewIssues  
Creation Baskets [Member]    
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]    
Number of units per basket   100,000uso_NumberOfUnitPerBasket
/ invest_InvestmentSecuritiesClassAxis
= uso_CreationBasketsMember
Redemption Baskets [Member]    
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]    
Number of units per basket   100,000uso_NumberOfUnitPerBasket
/ invest_InvestmentSecuritiesClassAxis
= uso_RedemptionBasketsMember
Open Futures Contracts, Long [Member] | United States [Member] | NYMEX WTI Crude Oil Futures CL February 2015 contracts, expiring January 2015    
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]    
Number of Contracts   58,662us-gaap_InvestmentOwnedBalanceContracts
/ invest_InvestmentGeographicRegionAxis
= country_US
/ invest_InvestmentSecuritiesSeriesAxis
= uso_NyMember
/ us-gaap_InvestmentTypeAxis
= uso_OpenFuturesContractsLongMember