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Contracts and Agreements (Brokerage Commission) (Detail) (USD $) | 3 Months Ended
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Mar. 31, 2015 | Mar. 31, 2014
Brokerage commissions | $ 1,187,217 us-gaap_FloorBrokerageExchangeAndClearanceFees | $ 264,164 us-gaap_FloorBrokerageExchangeAndClearanceFees
Rebalancing Investments Transaction [Member] |  |
Brokerage commissions | 958,970 us-gaap_FloorBrokerageExchangeAndClearanceFees / us-gaap_NatureOfExpenseAxis = uso_RebalancingInvestmentsTransactionMember | 132,435 us-gaap_FloorBrokerageExchangeAndClearanceFees / us-gaap_NatureOfExpenseAxis = uso_RebalancingInvestmentsTransactionMember
Percentage of average daily net assets | 80.77%uso_PercentageOfAverageDailyNetAssets / us-gaap_NatureOfExpenseAxis = uso_RebalancingInvestmentsTransactionMember | 50.13%uso_PercentageOfAverageDailyNetAssets / us-gaap_NatureOfExpenseAxis = uso_RebalancingInvestmentsTransactionMember
Creation And Redemption Activity [Member] |  |
Brokerage commissions | $ 228,247 us-gaap_FloorBrokerageExchangeAndClearanceFees / us-gaap_NatureOfExpenseAxis = uso_TradesNecessitatedByCreationAndRedemptionActivityMember | $ 131,729 us-gaap_FloorBrokerageExchangeAndClearanceFees / us-gaap_NatureOfExpenseAxis = uso_TradesNecessitatedByCreationAndRedemptionActivityMember
Percentage of average daily net assets | 19.23%uso_PercentageOfAverageDailyNetAssets / us-gaap_NatureOfExpenseAxis = uso_TradesNecessitatedByCreationAndRedemptionActivityMember | 49.87%uso_PercentageOfAverageDailyNetAssets / us-gaap_NatureOfExpenseAxis = uso_TradesNecessitatedByCreationAndRedemptionActivityMember
Commission [Member] |  |
Percentage of average daily net assets | 0.21%uso_PercentageOfAverageDailyNetAssets / us-gaap_NatureOfExpenseAxis = uso_CommissionMember | 0.16%uso_PercentageOfAverageDailyNetAssets / us-gaap_NatureOfExpenseAxis = uso_CommissionMember

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- Definition The amount of expense during the period for floor brokerage fees paid to other broker-dealers to execute trades on their behalf, stock exchange fees, order flow fees, and clearance fees. + References No definition available. + Details
Name: | us-gaap_FloorBrokerageExchangeAndClearanceFees
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Percentage of Average Daily Net Assets + References No definition available. + Details
Name: | uso_PercentageOfAverageDailyNetAssets
Namespace Prefix: | uso_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- Details
Name: | us-gaap_NatureOfExpenseAxis=uso_CommissionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_NatureOfExpenseAxis=uso_RebalancingInvestmentsTransactionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_NatureOfExpenseAxis=uso_TradesNecessitatedByCreationAndRedemptionActivityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |