Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

+ Details

Name:	us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The net realized gain (loss) on investments sold during the period, not including gains (losses) on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, which, for cash flow reporting, is a component of proceeds from investing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainLossOnSaleOfInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of open derivatives, commodity, or energy contracts, held at each balance sheet date, that was included in earnings for the period.

+ References

+ Details

Name:	us-gaap_UnrealizedGainLossOnDerivativesAndCommodityContracts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_CommodityContractMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	unl_DerivativeNatureAxis=unl_ClosedPositionsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_FutureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	unl_DerivativeNatureAxis=unl_OpenPositionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

FAIR VALUE OF FINANCIAL INSTRUMENTS (Effect of Derivative Instruments on Condensed Statements of Operations) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income	$ (916,739)	$ (2,118,314)	$ (2,576,807)	$ (4,399,140)
Change in Unrealized Gain (Loss) on Derivatives Recognized in Income			3,879,007	3,758,409
Commodity Contracts [Member] \| Realized gain (loss) on closed positions \| Future [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Realized Gain (Loss) on Derivatives Recognized in Income			(2,576,807)	(4,399,140)
Commodity Contracts [Member] \| Change in unrealized gain (loss) on open positions
Derivative Instruments, Gain (Loss) [Line Items]
Change in Unrealized Gain (Loss) on Derivatives Recognized in Income			$ 3,879,007	$ 3,758,409