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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

X

- Definition

Cash Equivalents, Maturity Period

+ References

No definition available.

+ Details

Name:	unl_CashEquivalentsMaturityPeriod
Namespace Prefix:	unl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- 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

X

- Details

Name:	unl_SignificantAccountingPoliciesLineItems
Namespace Prefix:	unl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration