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Condensed Schedule of Investments (USD $) | Mar. 31, 2015
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United State [Member] | Money Market Funds [Member] |  |
Market Values | $ 9,510,692 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember |
% of Partners' Capital | 55.93%unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember |
United State [Member] | Goldman Sachs Financial Square Funds - Government Fund - Class FS [Member] | Money Market Funds [Member] |  |
Unrealized Gain (Loss) on Open Commodity Contracts | 1 unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = unl_GoldmanSachsFinancialSquareFundsGovernmentFundClassFsMember | [1]
Principal Amount | 1 us-gaap_InvestmentOwnedBalancePrincipalAmount / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = unl_GoldmanSachsFinancialSquareFundsGovernmentFundClassFsMember | [1]
% of Partners' Capital | 0.00%unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = unl_GoldmanSachsFinancialSquareFundsGovernmentFundClassFsMember | [1]
Cash Equivalents [Member] | U.S. Treasury Bill, 0.06%, 4/30/2015 [Member] | US Treasury Securities [Member] |  |
Principal Amount | 3,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember / invest_InvestmentSecuritiesSeriesAxis = us-gaap_USTreasuryBillSecuritiesMember |
Market Values | 2,999,867 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember / invest_InvestmentSecuritiesSeriesAxis = us-gaap_USTreasuryBillSecuritiesMember |
% of Partners' Capital | 17.64%unl_PercentageOfPartnersCapital / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentSecuritiesClassAxis = us-gaap_USTreasurySecuritiesMember / invest_InvestmentSecuritiesSeriesAxis = us-gaap_USTreasuryBillSecuritiesMember |
Cash Equivalents [Member] | Morgan Stanley Institutional Liquidity Fund - Government Portfolio [Member] | Money Market Funds [Member] |  |
Principal Amount | 6,510,691 us-gaap_InvestmentOwnedBalancePrincipalAmount / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = unl_MorganStanleyInstitutionalLiquidityFundGovernmentPortfolioMember |
Market Values | 6,510,691 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = unl_MorganStanleyInstitutionalLiquidityFundGovernmentPortfolioMember |
% of Partners' Capital | 38.29%unl_PercentageOfPartnersCapital / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = unl_MorganStanleyInstitutionalLiquidityFundGovernmentPortfolioMember |
Cash Equivalents [Member] | Wells Fargo Advantage Government Money Market Fund - Class I [Member] | Money Market Funds [Member] |  |
Principal Amount | 3,000,000 us-gaap_InvestmentOwnedBalancePrincipalAmount / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = unl_WellsFargoAdvantageGovernmentMoneyMarketFundClassIMember |
Market Values | 3,000,000 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = unl_WellsFargoAdvantageGovernmentMoneyMarketFundClassIMember |
% of Partners' Capital | 17.64%unl_PercentageOfPartnersCapital / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentSecuritiesClassAxis = us-gaap_MoneyMarketFundsMember / invest_InvestmentSecuritiesSeriesAxis = unl_WellsFargoAdvantageGovernmentMoneyMarketFundClassIMember |
Cash Equivalents [Member] | United State [Member] |  |
Market Values | 12,510,559 us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US |
% of Partners' Capital | 73.57%unl_PercentageOfPartnersCapital / invest_InvestmentAxis = us-gaap_CashEquivalentsMember / invest_InvestmentGeographicRegionAxis = country_US |
Open Futures Contracts, Long [Member] | United State [Member] |  |
Number of Contracts | 584 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember | [2]
Unrealized Gain (Loss) on Open Commodity Contracts | (3,944,865)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember | [2]
% of Partners' Capital | (23.20%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember | [2]
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG May 2015 contracts, expiring April 2015 [Member] |  |
Number of Contracts | 48 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgOneMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (519,710)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgOneMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (3.06%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgOneMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG June 2015 contracts, expiring May 2015 [Member] |  |
Number of Contracts | 49 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgTwoMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (470,840)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgTwoMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (2.77%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgTwoMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG July 2015 contracts, expiring June 2015 [Member] |  |
Number of Contracts | 48 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgThreeMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (493,840)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgThreeMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (2.90%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgThreeMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG August 2015 contracts, expiring July 2015 [Member] |  |
Number of Contracts | 49 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgFourMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (422,970)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgFourMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (2.49%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgFourMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG September 2015 contracts, expiring August 2015 [Member] |  |
Number of Contracts | 49 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgFiveMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (376,940)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgFiveMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (2.22%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgFiveMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG October 2015 contracts, expiring September 2015 [Member] |  |
Number of Contracts | 49 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgSixMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (364,910)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgSixMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (2.14%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgSixMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG November 2015 contracts, expiring October 2015 [Member] |  |
Number of Contracts | 49 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgSevenMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (342,080)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgSevenMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (2.01%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgSevenMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG December 2015 contracts, expiring November 2015 [Member] |  |
Number of Contracts | 49 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgEightMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (355,050)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgEightMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (2.09%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgEightMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG January 2016 contracts, expiring December 2015 [Memer] |  |
Number of Contracts | 48 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgNineMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (309,900)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgNineMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (1.82%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgNineMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG February 2016 contracts, expiring January 2016 [Member] |  |
Number of Contracts | 49 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgTenMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (164,720)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgTenMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (0.97%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgTenMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG March 2016 contracts, expiring February 2016 [Member] |  |
Number of Contracts | 48 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgElevenMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | (89,745)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgElevenMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (0.53%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgElevenMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Open Futures Contracts, Long [Member] | United State [Member] | NYMEX Natural Gas Futures NG April 2016 contracts, expiring March 2016 [Member] |  |
Number of Contracts | 49 us-gaap_InvestmentOwnedBalanceContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgTwelveMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
Unrealized Gain (Loss) on Open Commodity Contracts | $ (34,160)unl_UnrealizedGainLossOnOpenCommodityFuturesAndClearedSwapContracts / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgTwelveMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
% of Partners' Capital | (0.20%)unl_PercentageOfPartnersCapital / invest_InvestmentGeographicRegionAxis = country_US / invest_InvestmentSecuritiesSeriesAxis = unl_NymexNaturalGasFuturesNgTwelveMember / us-gaap_InvestmentTypeAxis = unl_OpenFuturesContractsLongMember |
[1] | Represents less than 0.005%.
[2] | Collateral amounted to $5,231,739 on open futures contracts.

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