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FEES PAID BY THE FUND AND RELATED PARTY TRANSACTIONS - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fees Paid and Related Party Transactions [Line Items]
Percentage of Management Fee in Average Daily Total Net Assets	0.60%
Licensing fee incurred	$ 27,019	$ 8,433	$ 11,830
Investor tax reporting cost	172,800	131,500	144,700
Registration fees	124,835	0	0
Directors' fees and expenses	17,435	13,028	13,806
USL and the Related Public Funds, other than USCI, USAG, CPER and USMI
Fees Paid and Related Party Transactions [Line Items]
Directors' fees and expenses	$ 585,896	556,951	521,689
On and after October 20, 2011
Fees Paid and Related Party Transactions [Line Items]
Fee percentage	0.015%
USL's
Fees Paid and Related Party Transactions [Line Items]
Investor tax reporting cost		$ 13,028	$ 13,806

X

- Definition

Amount of registration fee expense for issuance of shares or units.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 220
-Section 45
-Paragraph 3
-Subparagraph (m)
-URI http://asc.fasb.org/extlink&oid=118262090&loc=SL114874205-224268

+ Details

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Balance Type:	debit
Period Type:	duration

X

- 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=120399700&loc=SL114874048-224260

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X

- 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=120395209&loc=SL114868664-224227

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Namespace Prefix:	us-gaap_
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Period Type:	duration

X

- Definition

Base Fee Percentage

+ References

No definition available.

+ Details

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X

- Definition

Fees Paid and Related Party Transactions [Line Items]

+ References

No definition available.

+ Details

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X

- Definition

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

+ References

No definition available.

+ Details

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Balance Type:	debit
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X

- Definition

Percentage of Management Fee In Average Daily Total Net Assets.

+ References

No definition available.

+ Details

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- Details

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- Details

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