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Contracts and Agreements (Brokerage Commission) (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Brokerage commissions	$ 1,187,217us-gaap_FloorBrokerageExchangeAndClearanceFees	$ 264,164us-gaap_FloorBrokerageExchangeAndClearanceFees
Rebalancing Investments Transaction [Member]
Brokerage commissions	958,970us-gaap_FloorBrokerageExchangeAndClearanceFees / us-gaap_NatureOfExpenseAxis = uso_RebalancingInvestmentsTransactionMember	132,435us-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	$ 228,247us-gaap_FloorBrokerageExchangeAndClearanceFees / us-gaap_NatureOfExpenseAxis = uso_TradesNecessitatedByCreationAndRedemptionActivityMember	$ 131,729us-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

X

- 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

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Balance Type:	debit
Period Type:	duration

X

- Definition

Percentage of Average Daily Net Assets

+ References

No definition available.

+ Details

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Namespace Prefix:	uso_
Data Type:	num:percentItemType
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Period Type:	instant

X

- Details

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X

- Details

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Period Type:

X

- Details

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