Condensed Statements of Operations (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Gain (loss) on trading of commodity futures contracts:
Realized gain (loss) on closed positions	$ (324,511,450)us-gaap_GainLossOnSaleOfInvestments	$ 27,074,999us-gaap_GainLossOnSaleOfInvestments
Change in unrealized gain (loss) on open positions	51,633,790us-gaap_UnrealizedGainLossOnInvestments	3,654,730us-gaap_UnrealizedGainLossOnInvestments
Dividend income	16,217us-gaap_DividendIncomeOperating	18,289us-gaap_DividendIncomeOperating
Interest income	194,598us-gaap_InterestIncomeOperating	53,246us-gaap_InterestIncomeOperating
ETF transaction fees	95,000us-gaap_FeesAndCommissions	91,000us-gaap_FeesAndCommissions
Total income (loss)	(272,571,845)us-gaap_Revenues	30,892,264us-gaap_Revenues
Expenses
General Partner management fees (Note 3)	2,557,917us-gaap_AssetManagementCosts	750,779us-gaap_AssetManagementCosts
Professional fees	214,577us-gaap_ProfessionalFees	227,545us-gaap_ProfessionalFees
Brokerage commissions	1,187,217	264,164
Directors' fees and insurance	68,084us-gaap_NoninterestExpenseDirectorsFees	44,892us-gaap_NoninterestExpenseDirectorsFees
License fees	85,264us-gaap_LicenseCosts	25,025us-gaap_LicenseCosts
Registration fees	5,339	500
Total expenses	4,118,398us-gaap_OperatingExpenses	1,312,905us-gaap_OperatingExpenses
Net income (loss)	$ (276,690,243)us-gaap_NetIncomeLoss	$ 29,579,359us-gaap_NetIncomeLoss
Net income (loss) per limited partnership share	$ (3.28)	$ 1.38
Net income (loss) per weighted average limited partnership share	$ (2.16)	$ 1.53
Weighted average limited partnership shares outstanding	128,206,667	19,293,333

The aggregate costs related to asset management during the reporting period.

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

- Definition

Amount of operating dividend income on securities.

+ 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 210.9-04.2)

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 2

-Article 9

+ Details

Name:	us-gaap_DividendIncomeOperating
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of fees and commissions from financial services and banking activities and correspondent clearing. Includes fees from depositor accounts, credit cards, merchant discounts, and fiduciary and trust activities, guarantee fees, investment advisory, management, and administrative fees, transfer agent fees, and insurance commissions.

+ 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 210.9-04.13)

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 13

-Article 9

+ Details

Name:	us-gaap_FeesAndCommissions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

- Definition

The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainLossOnSaleOfInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of operating interest income, including, but not limited to, amortization and accretion of premiums and discounts on securities.

+ References

+ Details

Name:	us-gaap_InterestIncomeOperating
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Costs incurred and are directly related to generating license revenue. Licensing arrangements include, but are not limited to, rights to use a patent, copyright, technology, manufacturing process, software or trademark.

+ References

+ Details

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

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Other Comprehensive Income

-URI http://asc.fasb.org/extlink&oid=6519514

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Net Income

-URI http://asc.fasb.org/extlink&oid=6518256

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.19)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.18)

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

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.22)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 8: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 19

-Article 5

Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 20

-Article 9

+ Details

Name:	us-gaap_NetIncomeLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Per unit of ownership amount after tax of income (loss) available to limited partnership (LP) unit-holder and units that would have been outstanding assuming the issuance of limited partner units for dilutive potential units outstanding.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187171-122770

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 4

-Section F

+ Details

Name:	us-gaap_NetIncomeLossNetOfTaxPerOutstandingLimitedPartnershipUnitDiluted
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Per unit of ownership amount after tax of income (loss) available to outstanding limited partnership (LP) unit-holder.

+ References

+ Details

Name:	us-gaap_NetIncomeLossPerOutstandingLimitedPartnershipUnitBasicNetOfTax
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Noninterest expense related to directors' fees which are fees paid by an Entity to its directors. Directors' fees may be paid in addition to salary and other benefits.

+ References

+ Details

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

- Definition

Generally recurring costs associated with normal operations except for the portion of these expenses which can be clearly related to production and included in cost of sales or services. Includes selling, general and administrative expense.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_OperatingExpensesAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

A fee charged for services from professionals such as doctors, lawyers and accountants. The term is often expanded to include other professions, for example, pharmacists charging to maintain a medicinal profile of a client or customer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.6-07.2(a),(b),(c),(d))

-URI http://asc.fasb.org/extlink&oid=6488393&loc=d3e606610-122999

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 946

-SubTopic 225

-Section 45

-Paragraph 3

-Subparagraph (k)

-URI http://asc.fasb.org/extlink&oid=6488370&loc=d3e13550-115849

+ Details

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

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ 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 210.5-03.1)

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

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 1

-Article 5

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period.

+ References

+ Details

Name:	us-gaap_UnrealizedGainLossOnInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Weighted average number of limited partnership units outstanding determined by relating the portion of time within a reporting period that limited partnership units have been outstanding to the total time in that period.

+ References

+ Details

Name:	us-gaap_WeightedAverageLimitedPartnershipUnitsOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	uso_GainLossOnCommodityFuturesAbstract
Namespace Prefix:	uso_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Registration Fees and Other Offering Expenses

+ References

No definition available.

+ Details

Name:	uso_RegistrationFeesAndOtherOfferingExpenses
Namespace Prefix:	uso_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration