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Contracts and Agreements (Additional Information) (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Annual fee for transfer agency services	$ 20,000us-gaap_NoninterestExpenseTransferAgentAndCustodianFees
Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Annual fee for custody, fund accounting and fund administration services	75,000us-gaap_CustodyFees / us-gaap_RangeAxis = us-gaap_MinimumMember
Transaction fees per transaction	7uso_TransactionFeesPaid / us-gaap_RangeAxis = us-gaap_MinimumMember
Commissions per round-turn trade, including applicable exchange and NFA fees for Oil Futures Contracts and options on Oil Futures Contracts	7uso_CommissionsPaid / us-gaap_RangeAxis = us-gaap_MinimumMember
Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Transaction fees per transaction	15uso_TransactionFeesPaid / us-gaap_RangeAxis = us-gaap_MaximumMember
Commissions per round-turn trade, including applicable exchange and NFA fees for Oil Futures Contracts and options on Oil Futures Contracts	15uso_CommissionsPaid / us-gaap_RangeAxis = us-gaap_MaximumMember
First $500 million of USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.06%uso_BaseFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupSixMember
Base amount for determining fee percentage	500,000,000uso_BasisAmountForFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupSixMember
USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets greater than $500 million but less than $1 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.0465%uso_BaseFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupSevenMember
USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets greater than $500 million but less than $1 billion [Member] | Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	500,000,000uso_BasisAmountForFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupSevenMember / us-gaap_RangeAxis = us-gaap_MinimumMember
USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets greater than $500 million but less than $1 billion [Member] | Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	1,000,000,000uso_BasisAmountForFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupSevenMember / us-gaap_RangeAxis = us-gaap_MaximumMember
USOF's, USNG's, US12OF's, UGA's, USDHO's, USSO's, US12NG's, USBO's, USCI's, CPER's, USAG's and USMI's combined net assets exceed $1 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.035%uso_BaseFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupEightMember
Base amount for determining fee percentage	1,000,000,000uso_BasisAmountForFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupEightMember
Marketing Agreement [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Marketing fee exclusive of the incentive fee	425,000us-gaap_MarketingExpense / us-gaap_TypeOfArrangementAxis = uso_MarketingAgreementMember
Marketing Agreement [Member] | USOF's assets from $0- $500 million [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.00%uso_BaseFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupThreeMember / us-gaap_TypeOfArrangementAxis = uso_MarketingAgreementMember
Marketing Agreement [Member] | USOF's assets from $0- $500 million [Member] | Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	0uso_BasisAmountForFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupThreeMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_TypeOfArrangementAxis = uso_MarketingAgreementMember
Marketing Agreement [Member] | USOF's assets from $0- $500 million [Member] | Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	500,000,000uso_BasisAmountForFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupThreeMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_TypeOfArrangementAxis = uso_MarketingAgreementMember
Marketing Agreement [Member] | USOF's assets from $500 million - $4 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.04%uso_BaseFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupFourMember / us-gaap_TypeOfArrangementAxis = uso_MarketingAgreementMember
Marketing Agreement [Member] | USOF's assets from $500 million - $4 billion [Member] | Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	500,000,000uso_BasisAmountForFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupFourMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_TypeOfArrangementAxis = uso_MarketingAgreementMember
Marketing Agreement [Member] | USOF's assets from $500 million - $4 billion [Member] | Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	4,000,000,000uso_BasisAmountForFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupFourMember / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_TypeOfArrangementAxis = uso_MarketingAgreementMember
Marketing Agreement [Member] | USOF's assets in excess of $4 billion [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Fee percentage	0.03%uso_BaseFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupFiveMember / us-gaap_TypeOfArrangementAxis = uso_MarketingAgreementMember
Ratio of expense to Average Net Assets	10.00%uso_RatioOfExpensesToAverageNetAssets / invest_InvestmentIdentifierSchemeAxis = uso_GroupFiveMember / us-gaap_TypeOfArrangementAxis = uso_MarketingAgreementMember
Marketing Agreement [Member] | USOF's assets in excess of $4 billion [Member] | Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Base amount for determining fee percentage	$ 4,000,000,000uso_BasisAmountForFeePercentage / invest_InvestmentIdentifierSchemeAxis = uso_GroupFiveMember / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_TypeOfArrangementAxis = uso_MarketingAgreementMember

X

- Definition

Those fees charged for services related to holding, advising, and managing customer investment assets. These account fees usually charged annually or semi-annually, on a per security basis, for the costs of services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.3)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

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Balance Type:	na
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X

- Definition

Expenditures for planning and executing the conception, pricing, promotion, and distribution of ideas, goods, and services. Costs of public relations and corporate promotions are typically considered to be marketing costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.4)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Fees paid to an agent employed by a corporation or mutual fund to maintain shareholder records, including purchases, sales, and account balances. Also includes custodian fees incurred during an accounting period from an agent, bank, trust company, or other organization that holds and safeguards an individual's, mutual fund's, or investment company's assets for them. These fees will be billed back to the client and are a component of noninterest expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.14)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

+ Details

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Balance Type:	debit
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X

- Definition

Base Fee Percentage

+ References

No definition available.

+ Details

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X

- Definition

Basis Amount for Fee Percentage

+ References

No definition available.

+ Details

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Namespace Prefix:	uso_
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Balance Type:	debit
Period Type:	instant

X

- Definition

Commissions Paid

+ References

No definition available.

+ Details

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Namespace Prefix:	uso_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Ratio Of Expenses To Average Net Assets

+ References

No definition available.

+ Details

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Namespace Prefix:	uso_
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Balance Type:	na
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X

- Definition

Transaction Fees Paid

+ References

No definition available.

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Namespace Prefix:	uso_
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Balance Type:	na
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- Details

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- Details

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X

- Details

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