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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Additional Information) (Details) |  | 6 Months Ended
--- | --- | ---
Feb. 29, 2012 Redemption Baskets [Member] | Feb. 29, 2012 Prior to February 29, 2012 [Member] Redemption Baskets [Member] | Jun. 30, 2013 Maximum [Member]
Significant Accounting Policies [Line Items] |  |  |
Number of units per basket | 50,000 | 100,000 |
Cash equivalents maturity period |  |  | 6 months

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- Definition Cash Equivalents, Maturity Period + References No definition available. + Details
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Namespace Prefix: | unl_
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- Definition Number of Units per Basket + References No definition available. + Details
Name: | unl_NumberOfUnitsPerBasket
Namespace Prefix: | unl_
Data Type: | us-types:perUnitItemType
Balance Type: | na
Period Type: | instant

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- Details
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Namespace Prefix: | unl_
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Period Type: | duration