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INVESTMENT IN UNCONSOLIDATED JOINT VENTURES (Details) (USD $) | 12 Months Ended | 0 Months Ended | 1 Months Ended | 0 Months Ended | 1 Months Ended | 0 Months Ended | 1 Months Ended | 12 Months Ended | 1 Months Ended | 0 Months Ended | 1 Months Ended | 3 Months Ended |  |  |  |  |  |  |  |
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Dec. 31, 2014 item | Dec. 31, 2013 | Dec. 31, 2012 | Oct. 18, 2013 | Oct. 28, 2009 | Oct. 28, 2009 | Oct. 31, 2009 | Apr. 30, 2008 | Feb. 01, 2015 item | Feb. 28, 2007 | Mar. 31, 2005 | Sep. 30, 2013 | Aug. 31, 2008 | Mar. 02, 2005 | Oct. 31, 2004 | Jan. 31, 2007 | Aug. 31, 2014 | Dec. 31, 2005 item | Jun. 30, 2013 | Dec. 15, 2011 | Oct. 02, 2011 | Aug. 02, 2011 | Aug. 17, 2010 | Apr. 30, 2012 | Feb. 29, 2012 | Dec. 31, 2010 | Oct. 03, 2005 item | Mar. 07, 2005 | Sep. 30, 2004 item | Dec. 31, 2006 | May 31, 2008 item | Aug. 31, 2004 item | Nov. 30, 2001 item | Dec. 31, 2011
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of limited partnerships and limited liability companies in which the entity has invested | 9 nen_InvestmentsInNumberOfLimitedPartnershipsAndLimitedLiabilityCompanies |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of partnerships investing in commercial property | 3 nen_NumberOfPartnershipsInvestingInCommercialProperties |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in joint venture | $ 8,807,868 us-gaap_EquityMethodInvestments | $ 12,025,142 us-gaap_EquityMethodInvestments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 196,071,540 us-gaap_SecuredDebt | 198,520,478 us-gaap_SecuredDebt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest paid | 8,791,000 us-gaap_InterestPaid | 8,062,000 us-gaap_InterestPaid | 7,776,000 us-gaap_InterestPaid |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on Sale of Real Estate |  | 3,678,839 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution to the Partnership | 3,858,386 us-gaap_PartnersCapitalAccountDistributions | 3,893,662 us-gaap_PartnersCapitalAccountDistributions | 3,932,410 us-gaap_PartnersCapitalAccountDistributions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Carrying value of investment to discontinue applying the equity method | 0 nen_EquityMethodInvestmentsAmountToDiscontinueApplyingEquityMethodForInvestment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Limited Partnerships |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution to the Partnership | 850,000 us-gaap_PartnersCapitalAccountDistributions / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_LimitedPartnershipsMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dexter Park |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in joint venture |  |  |  |  | 15,925,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 15,925,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 86,240,813 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 87,410,638 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 88,611,686 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership interest |  |  |  |  | 40.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 40.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 409 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 409 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 409 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase price of investments |  |  |  |  | 129,500,000 us-gaap_EquityMethodInvestmentAggregateCost / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 129,500,000 us-gaap_EquityMethodInvestmentAggregateCost / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments funded using cash reserves |  |  |  |  | 8,757,000 us-gaap_PaymentsToAcquireInterestInJointVenture / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capital contributions |  |  |  | 660,000 us-gaap_PartnersCapitalAccountContributions / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units retained for long-term investment | 409 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 409 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 409 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on Sale of Real Estate | 0 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units sold | 0 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Units to be sold | 0 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dexter Park | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 86,241,000 us-gaap_SecuredDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings |  |  |  |  |  |  | 89,914,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  | 5.57%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 5.57%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period for which the entity is required to make interest only payments |  |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortization period of debt |  |  |  |  |  | 30 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Bay Apartments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in joint venture |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,500,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 4,574,002 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember | 4,639,848 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember | 4,702,087 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |
Number of units | 48 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember | 48 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember | 48 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  | 20 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 168 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |
Purchase price of investments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30,875,000 us-gaap_EquityMethodInvestmentAggregateCost / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |
Number of units retained for long-term investment | 48 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember | 48 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember | 48 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  | 48 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 48 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |
Gain on Sale of Real Estate | 0 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units sold | 0 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Units to be sold | 0 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Bay Apartments | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 4,574,000 us-gaap_SecuredDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings |  |  |  |  |  |  |  | 2,368,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  | 5.75%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Bay Sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 0 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  | 1,668,000 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 120 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 120 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 120 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units retained for long-term investment | 0 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 0 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on Sale of Real Estate | 475,335 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units sold | 113 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 105 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 105 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Units left to sell | 7 nen_NumberOfUnitsLeftToSell / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 15 nen_NumberOfUnitsLeftToSell / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 15 nen_NumberOfUnitsLeftToSell / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  | 7 nen_NumberOfUnitsLeftToSell / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Units to be sold | 120 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 120 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 120 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Bay Sales | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings |  |  |  |  |  |  |  |  |  | 4,750,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  |  |  | 5.57%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period for which the entity is required to make interest only payments |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortization period of debt |  |  |  |  |  |  |  |  |  | 30 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Essex Development, LLC and Hamilton Essex 81, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in joint venture |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,000,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCAndHamiltonEssex81LLCMember |  |  |  |  |  |
Percentage of ownership interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCAndHamiltonEssex81LLCMember |  |  |  |  |  |
Purchase price of investments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 14,300,000 us-gaap_EquityMethodInvestmentAggregateCost / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCAndHamiltonEssex81LLCMember |  |  |  |  |  |
Hamilton Essex Development, LLC and Hamilton Essex 81, LLC | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings |  |  |  |  |  |  |  |  |  |  | 10,750,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCAndHamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Essex 81 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 8,109,676 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember | 8,234,548 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember | 8,352,317 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 49 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember | 49 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember | 49 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units retained for long-term investment | 49 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember | 49 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember | 49 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on Sale of Real Estate | 0 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units sold | 0 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Units to be sold | 0 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Essex 81 | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings | 8,110,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) | 5.79%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortization period of debt | 30 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Essex Development |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 1,987,830 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember | 2,041,146 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember | 2,093,184 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units retained for long-term investment | 1 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember | 1 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember | 1 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on Sale of Real Estate | 0 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units sold | 0 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Units to be sold | 0 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Essex Development | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings | 1,988,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contractual principal payments to be made | 4,443 us-gaap_DebtInstrumentPeriodicPaymentPrincipal / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  | 4,301 us-gaap_DebtInstrumentPeriodicPaymentPrincipal / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Margin over basis of interest rate (as a percent) | 2.25%us-gaap_DebtInstrumentBasisSpreadOnVariableRate1 / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Basis of interest rate |  | Libor |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional margin over basis of interest rate (as a percent) |  | 0.17%nen_DebtInstrumentNotionalBasisSpreadOnVariableRate / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cost associated with loan extension |  |  |  |  |  |  |  |  |  |  |  | 9,000 nen_DebtInstrumentCostOfExtensionOfLoan / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember | 6,000 nen_DebtInstrumentCostOfExtensionOfLoan / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Extended term of debt |  |  |  |  |  |  |  |  |  |  |  | 2 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum personal guaranty on mortgage |  |  |  |  |  |  |  |  |  |  |  |  | 1,000,000 us-gaap_GuaranteeObligationsMaximumExposure / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton 1025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in joint venture |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,352,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 4,806,039 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 4,869,583 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 4,934,741 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership interest |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 176 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 176 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 176 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  | 176 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase price of investments |  |  |  |  |  |  |  |  |  |  |  |  |  | 23,750,000 us-gaap_EquityMethodInvestmentAggregateCost / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units retained for long-term investment | 49 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 49 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 49 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  | 49 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on Sale of Real Estate | 0 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units sold | 127 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 127 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 127 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  | 127 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Units to be sold | 127 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 127 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 127 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton 1025 | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 4,806,000 us-gaap_SecuredDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,000,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  | 5.67%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period for which the entity is required to make interest only payments |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortization period of debt |  |  |  |  |  |  |  |  |  |  |  |  |  | 30 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of debt |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Minuteman |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in joint venture |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,075,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |
Outstanding amount of mortgage loan | 5,292,511 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember | 5,362,109 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember | 5,433,472 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |
Number of units | 42 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember | 42 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember | 42 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 42 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |
Purchase price of investments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10,100,000 us-gaap_EquityMethodInvestmentAggregateCost / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |
Number of units retained for long-term investment | 42 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember | 42 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember | 42 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on Sale of Real Estate | 0 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units sold | 0 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Units to be sold | 0 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount returned to partnership |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,775,000 us-gaap_ProceedsFromRepaymentsOfDebtMaturingInMoreThanThreeMonths / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton Minuteman | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 5,293,000 us-gaap_SecuredDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8,025,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember | 5,500,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5.67%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period for which the entity is required to make interest only payments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortization period of debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash contribution by the entity towards loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,250,000 nen_DebtInstrumentCashContributionByEntityTowardsDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |
Hamilton on Main Apts |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in joint venture |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 8,000,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |
Outstanding amount of mortgage loan | 16,900,000 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember | 15,317,643 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember | 15,611,045 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |
Number of units | 148 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember | 148 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember | 148 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 280 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |
Purchase price of investments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 56,000,000 us-gaap_EquityMethodInvestmentAggregateCost / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |
Number of units retained for long-term investment | 148 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember | 148 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember | 148 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on Sale of Real Estate | 0 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units sold | 0 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 137 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |
Units to be sold | 0 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton on Main Apts | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 16,900,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4.34%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hamilton on Main Apartments, LLC | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 16,825,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5.18%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period for which the entity is required to make interest only payments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortization period of debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term excluding period for which interest only payments to be made |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net proceeds after funding escrow accounts and closing costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 16,700,000 us-gaap_ProceedsFromDebtNetOfIssuanceCosts / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Refinanced amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15,205,000 nen_DebtInstrumentRefinancedAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Refinancing fees | 161,000 us-gaap_DebtIssuanceCosts / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
345 Franklin |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Investments in joint venture | 0 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,533,000 us-gaap_EquityMethodInvestments / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |
Outstanding amount of mortgage loan | 10,000,000 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember | 10,000,000 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember | 6,850,179 us-gaap_SecuredDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |
Number of units | 40 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember | 40 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember | 40 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 40 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |
Number of units retained for long-term investment | 40 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember | 40 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember | 40 nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayment of loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,776,000 us-gaap_RepaymentsOfDebt / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Gain on Sale of Real Estate | 0 us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units sold | 0 nen_NumberOfUnitsInRealEstatePropertySold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Units to be sold | 0 nen_NumberOfUnitsInRealEstatePropertyToBeSold / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Carrying value of investment to discontinue applying the equity method |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 nen_EquityMethodInvestmentsAmountToDiscontinueApplyingEquityMethodForInvestment / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
345 Franklin | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan | 10,000,000 us-gaap_SecuredDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.87%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period for which the entity is required to make interest only payments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amortization period of debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of debt |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Refinanced amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10,000,000 nen_DebtInstrumentRefinancedAmount / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Distribution to the Partnership |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,610,000 us-gaap_PartnersCapitalAccountDistributions / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential buildings | Dexter Park |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 409 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 409 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 409 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  | 409 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 409 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential buildings | Hamilton Bay Apartments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 48 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember | 48 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember | 48 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential buildings | Hamilton Bay Sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 120 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 120 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember | 120 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential buildings | Hamilton Essex 81 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 48 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember | 48 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember | 48 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential buildings | Hamilton Essex Development |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 0 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential buildings | Hamilton 1025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 175 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 175 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 175 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential buildings | Hamilton Minuteman |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 42 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember | 42 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember | 42 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential buildings | Hamilton on Main Apts |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 148 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember | 148 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember | 148 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Residential buildings | 345 Franklin |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 40 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember | 40 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember | 40 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_ResidentialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Apartment | Hamilton Essex Development, LLC and Hamilton Essex 81, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 48 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = nen_ResidentialApartmentMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCAndHamiltonEssex81LLCMember |  |  |  |  |  |
Commercial | Dexter Park |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 0 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commercial | Hamilton Bay Apartments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 0 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commercial | Hamilton Bay Sales |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 0 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commercial | Hamilton Essex Development, LLC and Hamilton Essex 81, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of properties |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 us-gaap_NumberOfRealEstateProperties / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCAndHamiltonEssex81LLCMember |  |  |  |  |  |
Commercial | Hamilton Essex 81 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssex81LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commercial | Hamilton Essex Development |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commercial | Hamilton 1025 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember | 1 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Hamilton1025LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commercial | Hamilton Minuteman |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 0 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonMinutemanLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commercial | Hamilton on Main Apts |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 0 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonOnMainLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Commercial | 345 Franklin |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of units | 0 us-gaap_NumberOfUnitsInRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = us-gaap_CommercialRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_Franklin345LLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Car parking lot | Hamilton Essex Development, LLC and Hamilton Essex 81, LLC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Capacity of real estate property (in cars per lot) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50 nen_CapacityOfRealEstateProperty / us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis = nen_CarParkingLotRealEstateMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonEssexDevelopmentLLCAndHamiltonEssex81LLCMember |  |  |  |  |  |
HBC |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Outstanding amount of mortgage loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,668,600 us-gaap_SecuredDebt / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember
Borrowings |  |  |  |  |  | 7,168,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  | 6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember | 6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of debt |  |  |  |  |  | 4 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notice period for principal paydown of debt |  |  |  |  |  | 6 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repayment of loan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 918,600 us-gaap_RepaymentsOfDebt / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember |  | 2,500,000 us-gaap_RepaymentsOfDebt / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember |  |  |  |  |  |  |  |
Contractual principal payments to be made |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,000,000 us-gaap_DebtInstrumentPeriodicPaymentPrincipal / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember | 1,000,000 us-gaap_DebtInstrumentPeriodicPaymentPrincipal / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember | 1,000,000 us-gaap_DebtInstrumentPeriodicPaymentPrincipal / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember |  |  | 750,000 us-gaap_DebtInstrumentPeriodicPaymentPrincipal / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember |  |  |  |  |  |  |  |  |
Interest paid |  |  | 18,960 us-gaap_InterestPaid / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Principal amount requested to be repaid |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,500,000 nen_DebtInstrumentEarlyPrincipalRepaymentAmountRequestedByLender / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember |  |  |  |  |  |  |  |  |  |  |
HBC | Dexter Park | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Borrowings |  |  |  |  |  |  | $ 7,168,000 us-gaap_ProceedsFromIssuanceOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) |  |  |  |  | 6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember | 6.00%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HBCHoldingsLLCMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonParkTowersLLCMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Term of debt |  |  |  |  |  | 4 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notice period for principal paydown of debt |  |  |  |  |  | 6 months |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Management Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of employees having ownership interest in the investment properties | 6 nen_NumberOfEmployeesHavingOwnershipInterest / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_ManagementCompanyMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) | 3.76%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_RangeAxis = us-gaap_MinimumMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum | Limited Partnerships |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership interest | 40.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_LimitedPartnershipsMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Minimum | Harold Brown |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership interest | 43.20%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_RangeAxis = us-gaap_MinimumMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HaroldBrownMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum | Mortgages payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interest rate (as a percent) | 5.97%us-gaap_DebtInstrumentInterestRateStatedPercentage / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_RangeAxis = us-gaap_MaximumMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum | Limited Partnerships |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership interest | 50.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_LimitedPartnershipsMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum | Harold Brown |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
INVESTMENT IN UNCONSOLIDATED JOINT VENTURES |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of ownership interest | 57.00%us-gaap_EquityMethodInvestmentOwnershipPercentage / us-gaap_RangeAxis = us-gaap_MaximumMember / us-gaap_RelatedPartyTransactionsByRelatedPartyAxis = nen_HaroldBrownMember |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

X
- Definition Represents the capacity of real estate property. + References No definition available. + Details
Name: | nen_CapacityOfRealEstateProperty
Namespace Prefix: | nen_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the amortization period of mortgage loan and its interest. + References No definition available. + Details
Name: | nen_DebtInstrumentAmortizationTerm
Namespace Prefix: | nen_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the cash contribution by the entity towards the debt. + References No definition available. + Details
Name: | nen_DebtInstrumentCashContributionByEntityTowardsDebt
Namespace Prefix: | nen_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the cost associated with the extension of mortgage loan. + References No definition available. + Details
Name: | nen_DebtInstrumentCostOfExtensionOfLoan
Namespace Prefix: | nen_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents the amount of principal to be repaid upon notice as per the request of the lender. + References No definition available. + Details
Name: | nen_DebtInstrumentEarlyPrincipalRepaymentAmountRequestedByLender
Namespace Prefix: | nen_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Represents the extended term of mortgage loan. + References No definition available. + Details
Name: | nen_DebtInstrumentExtendedTerm
Namespace Prefix: | nen_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the period of notice to be served in order to demand earlier payment of debt in whole or in part. + References No definition available. + Details
Name: | nen_DebtInstrumentNoticePeriodToDemandEarlyPayment
Namespace Prefix: | nen_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The notional percentage points added to the reference rate to compute the variable rate on the debt instrument. + References No definition available. + Details
Name: | nen_DebtInstrumentNotionalBasisSpreadOnVariableRate
Namespace Prefix: | nen_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the amount of debt obligation refinanced by the entity. + References No definition available. + Details
Name: | nen_DebtInstrumentRefinancedAmount
Namespace Prefix: | nen_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Represents the term excluding period for which interest only payments are to be made. + References No definition available. + Details
Name: | nen_DebtInstrumentTermExcludingTermForWhichInterestOnlyPaymentsRequired
Namespace Prefix: | nen_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the period for which the entity is required to make interest only payments on the debt instrument. + References No definition available. + Details
Name: | nen_DebtInstrumentTermForWhichInterestOnlyPaymentsRequired
Namespace Prefix: | nen_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the carrying value of investment as of the balance sheet date to discontinue applying the equity method. + References No definition available. + Details
Name: | nen_EquityMethodInvestmentsAmountToDiscontinueApplyingEquityMethodForInvestment
Namespace Prefix: | nen_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the number of limited partnerships and limited liability companies in which the entity has made investments. + References No definition available. + Details
Name: | nen_InvestmentsInNumberOfLimitedPartnershipsAndLimitedLiabilityCompanies
Namespace Prefix: | nen_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of employees other than the President having an ownership interest. + References No definition available. + Details
Name: | nen_NumberOfEmployeesHavingOwnershipInterest
Namespace Prefix: | nen_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of partnerships which are investing in commercial properties. + References No definition available. + Details
Name: | nen_NumberOfPartnershipsInvestingInCommercialProperties
Namespace Prefix: | nen_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of units retained for long-term investment. + References No definition available. + Details
Name: | nen_NumberOfUnitsInRealEstatePropertyRetainedForLongTermInvestment
Namespace Prefix: | nen_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the number of units sold. + References No definition available. + Details
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