CONTRACTS AND AGREEMENTS (Additional Information) (Detail)	12 Months Ended
Dec. 31, 2018 USD ($) $ / Unit
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Annual fee for custody, fund accounting and fund administration services	$ 75,000
Marketing Agreement [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Marketing fee exclusive of the incentive fee	$ 425,000
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%
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	$ 0
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	$ 500,000,000
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%
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	$ 500,000,000
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	$ 4,000,000,000
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%
Ratio of expense to Average Net Assets	10.00%
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	$ 4,000,000,000
Brown Brothers Harriman & Co. Agreements [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Annual fee for transfer agency services	20,000
Brown Brothers Harriman & Co. Agreements [Member] \| Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Annual fee for custody, fund accounting and fund administration services	$ 75,000
Transaction fees per transaction \| $ / Unit	7
Brown Brothers Harriman & Co. Agreements [Member] \| Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Transaction fees per transaction \| $ / Unit	15
Brown Brothers Harriman & Co. Agreements [Member] \| 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%
Base amount for determining fee percentage	$ 500,000,000
Brown Brothers Harriman & Co. Agreements [Member] \| 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%
Brown Brothers Harriman & Co. Agreements [Member] \| 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	$ 500,000,000
Brown Brothers Harriman & Co. Agreements [Member] \| 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	$ 1,000,000,000
Brown Brothers Harriman & Co. Agreements [Member] \| 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%
Base amount for determining fee percentage	$ 1,000,000,000
Brokerage and Futures Commission Merchant Agreements [Member] \| Minimum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Commissions per round-turn trade, including applicable exchange and NFA fees for Oil Futures Contracts and options on Oil Futures Contracts \| $ / Unit	7
Brokerage and Futures Commission Merchant Agreements [Member] \| Maximum [Member]
Long-Duration Contracts, Assumptions by Product and Guarantee [Line Items]
Commissions per round-turn trade, including applicable exchange and NFA fees for Oil Futures Contracts and options on Oil Futures Contracts \| $ / Unit	8

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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.3)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.14)
-URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260

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Base Fee Percentage

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