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.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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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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

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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Namespace Prefix:	us-gaap_
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Balance Type:	debit
Period Type:	duration

- Definition

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

+ References

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 210.5-03.6)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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Balance Type:	debit
Period Type:	duration

- Definition

Base Fee Percentage

+ References

No definition available.

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Namespace Prefix:	usl_
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Balance Type:	na
Period Type:	duration

- Definition

Fees Paid and Related Party Transactions [Line Items]

+ References

No definition available.

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Namespace Prefix:	usl_
Data Type:	xbrli:stringItemType
Balance Type:	na
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- Definition

It represent the value of license fees and other offering expenses.

+ References

No definition available.

+ Details

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Namespace Prefix:	usl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	invest_InvestmentIdentifierSchemeAxis=usl_FundTrustsMember
Namespace Prefix:
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FEES PAID BY THE FUND AND RELATED PARTY TRANSACTIONS (Additional Information) (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2019
Fees Paid and Related Party Transactions [Line Items]
USCF Management Fee	USL is contractually obligated to pay USCF a fee, which is paid monthly, equal to 0.60% per annum of average daily total net assets.
Licensing fee incurred	$ 2,215	$ 3,182
Estimated directors' fees and expenses	$ 3,267	$ 3,231
Scenario, Forecast [Member]
Fees Paid and Related Party Transactions [Line Items]
Estimated investor tax reporting cost			$ 105,000
Estimated directors' fees and expenses			14,300
USL and the Related Public Funds, other than USCI, USAG, CPER and USMI \| Scenario, Forecast [Member]
Fees Paid and Related Party Transactions [Line Items]
Estimated directors' fees and expenses			$ 545,250
On and after October 20, 2011
Fees Paid and Related Party Transactions [Line Items]
Fee percentage	0.015%