FEES PAID BY THE FUND AND RELATED PARTY TRANSACTIONS - (Additional Information) (Details) (USD $)	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Fees Paid and Related Party Transactions [Line Items]
USCF Management Fee	UNL is contractually obligated to pay USCF a fee, which is paid monthly, equal to 0.75% per annum of average daily total net assets
Estimated directors fees and expenses	$ 1,032us-gaap_NoninterestExpenseDirectorsFees	$ 1,780us-gaap_NoninterestExpenseDirectorsFees
Licensing fee incurred	649us-gaap_LicenseCosts	894us-gaap_LicenseCosts
Expense waiver (Note 3)	17,835unl_ExpenseWaiver	38,045unl_ExpenseWaiver
Licensing Agreements [Member] \| On and after October 20, 2011 [Member]
Fees Paid and Related Party Transactions [Line Items]
Fee percentage	0.015%
Assets basis for determining fee percentage	on all net assets
Future Period - for the year ending December 31, 2014 [Member]
Fees Paid and Related Party Transactions [Line Items]
Estimated investor tax reporting cost	86,000
Future Period - for the year ending December 31, 2014 [Member] \| Maximum [Member]
Fees Paid and Related Party Transactions [Line Items]
Costs and expenses annual limit for reimbursement	0.15%
UNL [Member] \| Related Public Funds [Member]
Fees Paid and Related Party Transactions [Line Items]
Estimated directors fees and expenses	$ 4,644	$ 560,625

Base Amount For Fee Percentage

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- Definition

Base Fee Percentage

+ References

No definition available.

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- Definition

Expense Waiver

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- Definition

Percentage of Change in Costs and Expenses

+ References

No definition available.

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- 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

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- Definition

Description of the nature of payments to managing member or general partner for management of the day-to-day business functions of the limited liability company (LLC) or limited partnership (LP), including the fee rate, basis of calculation, relevant accounting period, whether the fee is paid to an entity other than the managing member or general partner, or whether the fee is waived.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 850

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864

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- 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

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

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- Definition

Amount of general expenses not normally included in Other Operating Costs and Expenses.

+ 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 210.5-03.6)

-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 6

-Article 5

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