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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Additional Information) (Details)	Mar. 31, 2015
Significant Accounting Policies [Line Items]
Fee paid by Authorized Purchasers for each order placed to create one or more Creation Baskets or to redeem one or more baskets	350unl_FeePaidPerOrder
Redemption Baskets [Member]
Significant Accounting Policies [Line Items]
Number of units per basket	50,000unl_NumberOfUnitsPerBasket / invest_InvestmentSecuritiesClassAxis = unl_RedemptionBasketsMember

X

- Definition

Fee Paid Per Order

+ References

No definition available.

+ Details

Name:	unl_FeePaidPerOrder
Namespace Prefix:	unl_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	instant

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

X

- Details

Name:	invest_InvestmentSecuritiesClassAxis=unl_RedemptionBasketsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: