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FEES PAID BY THE FUND AND RELATED PARTY TRANSACTIONS - Additional Information (Details) - USD ($) | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2019
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |
Percentage of management fee in average daily total net assets |  |  | 0.60% |  |
Licensing fee incurred | $ 2,189 | $ 3,165 | $ 4,404 | $ 6,347 |
Estimated directors' fees and expenses | $ 2,738 | $ 3,583 | $ 6,005 | $ 6,814 |
Scenario Forecast |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |
Estimated investor tax reporting cost |  |  |  |  | $ 100,000
Estimated directors' fees and expenses |  |  |  |  | 13,000
USL and the Related Public Funds, other than USCI, USAG, CPER and USMI | Scenario Forecast |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |
Estimated directors' fees and expenses |  |  |  |  | $ 543,500
On and after October 20, 2011 |  |  |  |  |
Fees Paid and Related Party Transactions [Line Items] |  |  |  |  |
Fee percentage |  |  | 0.015% |  |

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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://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 + Details
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- 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 + Details
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