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RENTAL PROPERTIES (Details 2) (USD $) | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Rental Properties |  |  |
Balance, Beginning | $ 221,454,286 us-gaap_RealEstateGrossAtCarryingValue | $ 158,624,893 us-gaap_RealEstateGrossAtCarryingValue | $ 159,123,799 us-gaap_RealEstateGrossAtCarryingValue
Additions: |  |  |
Buildings, improvements and other assets | 5,604,791 us-gaap_OtherRealEstateImprovements | 65,349,698 us-gaap_OtherRealEstateImprovements | 2,360,399 us-gaap_OtherRealEstateImprovements
Balance before deductions | 227,059,077 nen_RealEstateBeforeDeductions | 223,974,591 nen_RealEstateBeforeDeductions | 161,484,198 nen_RealEstateBeforeDeductions
Deduct |  |  |
Write-offs of retired or disposed assets | 2,037,131 nen_RealEstateCostOfRealEstateRetiredOrDisposed | 2,505,787 nen_RealEstateCostOfRealEstateRetiredOrDisposed | 1,607,830 nen_RealEstateCostOfRealEstateRetiredOrDisposed
Rental properties held for sale and/or sold |  | 14,518 nen_RealEstateCostOfRealEstateSoldOrHeldForSale | 1,251,475 nen_RealEstateCostOfRealEstateSoldOrHeldForSale
Balance, Ending | 225,021,946 us-gaap_RealEstateGrossAtCarryingValue | 221,454,286 us-gaap_RealEstateGrossAtCarryingValue | 158,624,893 us-gaap_RealEstateGrossAtCarryingValue
Accumulated Depreciation |  |  |
Balance, Beginning | 68,549,625 us-gaap_RealEstateAccumulatedDepreciation | 63,651,293 us-gaap_RealEstateAccumulatedDepreciation | 60,199,265 us-gaap_RealEstateAccumulatedDepreciation
Add: |  |  |
Depreciation for the year | 9,393,368 us-gaap_SECScheduleIIIRealEstateAccumulatedDepreciationDepreciationExpense | 7,404,120 us-gaap_SECScheduleIIIRealEstateAccumulatedDepreciationDepreciationExpense | 5,849,083 us-gaap_SECScheduleIIIRealEstateAccumulatedDepreciationDepreciationExpense
Total additions | 77,942,993 nen_RealEstateAccumulatedDepreciationAdditionsTotal | 71,055,413 nen_RealEstateAccumulatedDepreciationAdditionsTotal | 66,048,348 nen_RealEstateAccumulatedDepreciationAdditionsTotal
Deduct: |  |  |
Accumulated depreciation of retired or disposed assets | 2,037,131 nen_RealEstateAccumulatedDepreciationRealEstateRetiredOrDisposed | 2,505,788 nen_RealEstateAccumulatedDepreciationRealEstateRetiredOrDisposed | 1,607,830 nen_RealEstateAccumulatedDepreciationRealEstateRetiredOrDisposed
Accumulated depreciation of rental properties held for sale and/or sold |  |  | 789,225 nen_RealEstateAccumulatedDepreciationRealEstateSoldOrHeldForSale
Balance, Ending | 75,905,862 us-gaap_RealEstateAccumulatedDepreciation | 68,549,625 us-gaap_RealEstateAccumulatedDepreciation | 63,651,293 us-gaap_RealEstateAccumulatedDepreciation
Encumbrances (First Mortgages) | 196,071,540 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances |  |
Initial Cost to Partnerships |  |  |
Land | 41,773,766 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand |  |
Building Improvements | 150,044,184 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 33,248,189 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 41,729,573 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand |  |
Building Improvements | 183,292,373 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements |  |
Totals | 225,021,946 us-gaap_RealEstateGrossAtCarryingValue | 221,454,286 us-gaap_RealEstateGrossAtCarryingValue | 158,624,893 us-gaap_RealEstateGrossAtCarryingValue
Accumulated Depreciation | 75,905,862 us-gaap_RealEstateAccumulatedDepreciation | 68,549,625 us-gaap_RealEstateAccumulatedDepreciation | 63,651,293 us-gaap_RealEstateAccumulatedDepreciation
Buildings and Improvements | Minimum |  |  |
Gross Amount at Which Carried at Close of Period |  |  |
Estimated useful lives | 10 years |  |
Buildings and Improvements | Maximum |  |  |
Gross Amount at Which Carried at Close of Period |  |  |
Estimated useful lives | 39 years |  |
Other Categories of Assets | Minimum |  |  |
Gross Amount at Which Carried at Close of Period |  |  |
Estimated useful lives | 5 years |  |
Other Categories of Assets | Maximum |  |  |
Gross Amount at Which Carried at Close of Period |  |  |
Estimated useful lives | 15 years |  |
Boylston Downtown L.P. Residential Apartments Boston, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 18,386,522 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BoylstonDowntownLPResidentialApartmentsBostonMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 10,220,358 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BoylstonDowntownLPResidentialApartmentsBostonMassachusettsMember |  |
Encumbrances (First Mortgages) | 40,000,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BoylstonDowntownLPResidentialApartmentsBostonMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 2,112,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BoylstonDowntownLPResidentialApartmentsBostonMassachusettsMember |  |
Building Improvements | 8,593,109 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BoylstonDowntownLPResidentialApartmentsBostonMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 7,681,413 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BoylstonDowntownLPResidentialApartmentsBostonMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 2,112,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BoylstonDowntownLPResidentialApartmentsBostonMassachusettsMember |  |
Building Improvements | 16,274,522 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BoylstonDowntownLPResidentialApartmentsBostonMassachusettsMember |  |
Totals | 18,386,522 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BoylstonDowntownLPResidentialApartmentsBostonMassachusettsMember |  |
Accumulated Depreciation | 10,220,358 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BoylstonDowntownLPResidentialApartmentsBostonMassachusettsMember |  |
Brookside Associates LLC Residential Apartments Woburn, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 4,264,970 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BrooksideAssociatesLLCResidentialApartmentsWoburnMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 1,858,026 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BrooksideAssociatesLLCResidentialApartmentsWoburnMassachusettsMember |  |
Encumbrances (First Mortgages) | 2,642,649 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BrooksideAssociatesLLCResidentialApartmentsWoburnMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 684,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BrooksideAssociatesLLCResidentialApartmentsWoburnMassachusettsMember |  |
Building Improvements | 3,116,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BrooksideAssociatesLLCResidentialApartmentsWoburnMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 464,970 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BrooksideAssociatesLLCResidentialApartmentsWoburnMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 684,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BrooksideAssociatesLLCResidentialApartmentsWoburnMassachusettsMember |  |
Building Improvements | 3,580,970 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BrooksideAssociatesLLCResidentialApartmentsWoburnMassachusettsMember |  |
Totals | 4,264,970 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BrooksideAssociatesLLCResidentialApartmentsWoburnMassachusettsMember |  |
Accumulated Depreciation | 1,858,026 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_BrooksideAssociatesLLCResidentialApartmentsWoburnMassachusettsMember |  |
Clovelly Apartments L.P. Residential Apartments Nashua, New Hampshire |  |  |
Deduct |  |  |
Balance, Ending | 3,317,241 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ClovellyApartmentsLPResidentialApartmentsNashuaNewHampshireMember |  |
Deduct: |  |  |
Balance, Ending | 2,081,134 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ClovellyApartmentsLPResidentialApartmentsNashuaNewHampshireMember |  |
Encumbrances (First Mortgages) | 4,160,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ClovellyApartmentsLPResidentialApartmentsNashuaNewHampshireMember |  |
Initial Cost to Partnerships |  |  |
Land | 177,610 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ClovellyApartmentsLPResidentialApartmentsNashuaNewHampshireMember |  |
Building Improvements | 1,478,359 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ClovellyApartmentsLPResidentialApartmentsNashuaNewHampshireMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 1,661,272 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ClovellyApartmentsLPResidentialApartmentsNashuaNewHampshireMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 177,610 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ClovellyApartmentsLPResidentialApartmentsNashuaNewHampshireMember |  |
Building Improvements | 3,139,631 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ClovellyApartmentsLPResidentialApartmentsNashuaNewHampshireMember |  |
Totals | 3,317,241 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ClovellyApartmentsLPResidentialApartmentsNashuaNewHampshireMember |  |
Accumulated Depreciation | 2,081,134 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ClovellyApartmentsLPResidentialApartmentsNashuaNewHampshireMember |  |
Commonwealth 1137 L.P. Residential Apartments Boston, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 2,893,182 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1137LPResidentialApartmentsBostonMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 1,416,545 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1137LPResidentialApartmentsBostonMassachusettsMember |  |
Encumbrances (First Mortgages) | 3,750,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1137LPResidentialApartmentsBostonMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 342,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1137LPResidentialApartmentsBostonMassachusettsMember |  |
Building Improvements | 1,367,669 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1137LPResidentialApartmentsBostonMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 1,183,513 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1137LPResidentialApartmentsBostonMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 342,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1137LPResidentialApartmentsBostonMassachusettsMember |  |
Building Improvements | 2,551,182 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1137LPResidentialApartmentsBostonMassachusettsMember |  |
Totals | 2,893,182 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1137LPResidentialApartmentsBostonMassachusettsMember |  |
Accumulated Depreciation | 1,416,545 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1137LPResidentialApartmentsBostonMassachusettsMember |  |
Commonwealth 1144 L.P. Residential Apartments Boston, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 9,149,680 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1144LPResidentialApartmentsBostonMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 4,851,194 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1144LPResidentialApartmentsBostonMassachusettsMember |  |
Encumbrances (First Mortgages) | 14,780,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1144LPResidentialApartmentsBostonMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 1,410,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1144LPResidentialApartmentsBostonMassachusettsMember |  |
Building Improvements | 5,664,816 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1144LPResidentialApartmentsBostonMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 2,074,864 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1144LPResidentialApartmentsBostonMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 1,410,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1144LPResidentialApartmentsBostonMassachusettsMember |  |
Building Improvements | 7,739,680 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1144LPResidentialApartmentsBostonMassachusettsMember |  |
Totals | 9,149,680 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1144LPResidentialApartmentsBostonMassachusettsMember |  |
Accumulated Depreciation | 4,851,194 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_Commonwealth1144LPResidentialApartmentsBostonMassachusettsMember |  |
Executive Apartments L.P. Residential Apartments Framingham, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 1,504,045 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ExecutiveApartmentsLPResidentialApartmentsFraminghamMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 1,056,717 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ExecutiveApartmentsLPResidentialApartmentsFraminghamMassachusettsMember |  |
Encumbrances (First Mortgages) | 2,415,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ExecutiveApartmentsLPResidentialApartmentsFraminghamMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 91,400 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ExecutiveApartmentsLPResidentialApartmentsFraminghamMassachusettsMember |  |
Building Improvements | 740,360 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ExecutiveApartmentsLPResidentialApartmentsFraminghamMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 672,285 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ExecutiveApartmentsLPResidentialApartmentsFraminghamMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 91,400 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ExecutiveApartmentsLPResidentialApartmentsFraminghamMassachusettsMember |  |
Building Improvements | 1,412,645 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ExecutiveApartmentsLPResidentialApartmentsFraminghamMassachusettsMember |  |
Totals | 1,504,045 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ExecutiveApartmentsLPResidentialApartmentsFraminghamMassachusettsMember |  |
Accumulated Depreciation | 1,056,717 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_ExecutiveApartmentsLPResidentialApartmentsFraminghamMassachusettsMember |  |
Hamilton Battle Green LLC Residential Apartments Lexington, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 9,928,822 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonBattleGreenLLCResidentialApartmentsLexingtonMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 1,409,607 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonBattleGreenLLCResidentialApartmentsLexingtonMassachusettsMember |  |
Encumbrances (First Mortgages) | 4,736,891 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonBattleGreenLLCResidentialApartmentsLexingtonMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 1,341,737 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonBattleGreenLLCResidentialApartmentsLexingtonMassachusettsMember |  |
Building Improvements | 8,457,497 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonBattleGreenLLCResidentialApartmentsLexingtonMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 129,588 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonBattleGreenLLCResidentialApartmentsLexingtonMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 1,341,737 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonBattleGreenLLCResidentialApartmentsLexingtonMassachusettsMember |  |
Building Improvements | 8,587,085 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonBattleGreenLLCResidentialApartmentsLexingtonMassachusettsMember |  |
Totals | 9,928,822 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonBattleGreenLLCResidentialApartmentsLexingtonMassachusettsMember |  |
Accumulated Depreciation | 1,409,607 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonBattleGreenLLCResidentialApartmentsLexingtonMassachusettsMember |  |
Hamilton Cypress LLC Commercial-1031Exchange Brookline, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 7,227,431 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonCypressLLCCommercial1031ExchangeBrooklineMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 878,739 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonCypressLLCCommercial1031ExchangeBrooklineMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 2,362,596 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonCypressLLCCommercial1031ExchangeBrooklineMassachusettsMember |  |
Building Improvements | 4,613,985 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonCypressLLCCommercial1031ExchangeBrooklineMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 250,850 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonCypressLLCCommercial1031ExchangeBrooklineMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 2,362,596 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonCypressLLCCommercial1031ExchangeBrooklineMassachusettsMember |  |
Building Improvements | 4,864,835 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonCypressLLCCommercial1031ExchangeBrooklineMassachusettsMember |  |
Totals | 7,227,431 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonCypressLLCCommercial1031ExchangeBrooklineMassachusettsMember |  |
Accumulated Depreciation | 878,739 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonCypressLLCCommercial1031ExchangeBrooklineMassachusettsMember |  |
Hamilton Green Apartments Residential Apartments Andover, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 61,402,078 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonGreenApartmentsResidentialApartmentsAndoverMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 4,931,941 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonGreenApartmentsResidentialApartmentsAndoverMassachusettsMember |  |
Encumbrances (First Mortgages) | 38,500,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonGreenApartmentsResidentialApartmentsAndoverMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 16,054,336 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonGreenApartmentsResidentialApartmentsAndoverMassachusettsMember |  |
Building Improvements | 44,794,438 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonGreenApartmentsResidentialApartmentsAndoverMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 553,304 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonGreenApartmentsResidentialApartmentsAndoverMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 16,054,336 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonGreenApartmentsResidentialApartmentsAndoverMassachusettsMember |  |
Building Improvements | 45,347,742 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonGreenApartmentsResidentialApartmentsAndoverMassachusettsMember |  |
Totals | 61,402,078 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonGreenApartmentsResidentialApartmentsAndoverMassachusettsMember |  |
Accumulated Depreciation | 4,931,941 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonGreenApartmentsResidentialApartmentsAndoverMassachusettsMember |  |
Hamilton Linewt LLC Commercial-1031Exchange Newton, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 3,598,777 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonLinewtLLCCommercial1031ExchangeNewtonMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 492,424 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonLinewtLLCCommercial1031ExchangeNewtonMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 884,042 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonLinewtLLCCommercial1031ExchangeNewtonMassachusettsMember |  |
Building Improvements | 2,652,127 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonLinewtLLCCommercial1031ExchangeNewtonMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 62,608 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonLinewtLLCCommercial1031ExchangeNewtonMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 884,042 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonLinewtLLCCommercial1031ExchangeNewtonMassachusettsMember |  |
Building Improvements | 2,714,735 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonLinewtLLCCommercial1031ExchangeNewtonMassachusettsMember |  |
Totals | 3,598,777 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonLinewtLLCCommercial1031ExchangeNewtonMassachusettsMember |  |
Accumulated Depreciation | 492,424 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonLinewtLLCCommercial1031ExchangeNewtonMassachusettsMember |  |
Hamilton Oaks Associates LLC Residential Apartments Brockton, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 16,638,080 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonOaksAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 8,036,862 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonOaksAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Encumbrances (First Mortgages) | 11,925,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonOaksAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 2,175,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonOaksAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Building Improvements | 12,325,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonOaksAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 2,138,080 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonOaksAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 2,175,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonOaksAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Building Improvements | 14,463,080 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonOaksAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Totals | 16,638,080 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonOaksAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Accumulated Depreciation | 8,036,862 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonOaksAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Highland Street Apartment, L.P. Residential Apartments Lowell, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 1,164,232 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HighlandStreetApartmentLPResidentialApartmentsLowellMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 629,766 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HighlandStreetApartmentLPResidentialApartmentsLowellMassachusettsMember |  |
Encumbrances (First Mortgages) | 1,050,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HighlandStreetApartmentLPResidentialApartmentsLowellMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 156,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HighlandStreetApartmentLPResidentialApartmentsLowellMassachusettsMember |  |
Building Improvements | 634,085 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HighlandStreetApartmentLPResidentialApartmentsLowellMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 374,147 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HighlandStreetApartmentLPResidentialApartmentsLowellMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 156,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HighlandStreetApartmentLPResidentialApartmentsLowellMassachusettsMember |  |
Building Improvements | 1,008,232 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HighlandStreetApartmentLPResidentialApartmentsLowellMassachusettsMember |  |
Totals | 1,164,232 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HighlandStreetApartmentLPResidentialApartmentsLowellMassachusettsMember |  |
Accumulated Depreciation | 629,766 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HighlandStreetApartmentLPResidentialApartmentsLowellMassachusettsMember |  |
Linhart L.P. Residential/Commercial Newton, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 3,203,713 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_LinhartLPResidentialCommercialNewtonMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 1,945,771 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_LinhartLPResidentialCommercialNewtonMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 385,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_LinhartLPResidentialCommercialNewtonMassachusettsMember |  |
Building Improvements | 1,540,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_LinhartLPResidentialCommercialNewtonMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 1,278,713 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_LinhartLPResidentialCommercialNewtonMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 385,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_LinhartLPResidentialCommercialNewtonMassachusettsMember |  |
Building Improvements | 2,818,713 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_LinhartLPResidentialCommercialNewtonMassachusettsMember |  |
Totals | 3,203,713 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_LinhartLPResidentialCommercialNewtonMassachusettsMember |  |
Accumulated Depreciation | 1,945,771 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_LinhartLPResidentialCommercialNewtonMassachusettsMember |  |
NERA Dean St. Associates LLC Residential Apartments Norwood, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 8,004,571 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NERADeanStAssociatesLLCResidentialApartmentsNorwoodMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 2,893,369 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NERADeanStAssociatesLLCResidentialApartmentsNorwoodMassachusettsMember |  |
Encumbrances (First Mortgages) | 5,687,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NERADeanStAssociatesLLCResidentialApartmentsNorwoodMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 1,512,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NERADeanStAssociatesLLCResidentialApartmentsNorwoodMassachusettsMember |  |
Building Improvements | 5,701,480 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NERADeanStAssociatesLLCResidentialApartmentsNorwoodMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 791,091 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NERADeanStAssociatesLLCResidentialApartmentsNorwoodMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 1,512,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NERADeanStAssociatesLLCResidentialApartmentsNorwoodMassachusettsMember |  |
Building Improvements | 6,492,571 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NERADeanStAssociatesLLCResidentialApartmentsNorwoodMassachusettsMember |  |
Totals | 8,004,571 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NERADeanStAssociatesLLCResidentialApartmentsNorwoodMassachusettsMember |  |
Accumulated Depreciation | 2,893,369 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NERADeanStAssociatesLLCResidentialApartmentsNorwoodMassachusettsMember |  |
North Beacon 140 L.P. Residential Units Boston, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 6,516,240 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NorthBeacon140LPResidentialUnitsBostonMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 3,476,883 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NorthBeacon140LPResidentialUnitsBostonMassachusettsMember |  |
Encumbrances (First Mortgages) | 6,937,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NorthBeacon140LPResidentialUnitsBostonMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 936,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NorthBeacon140LPResidentialUnitsBostonMassachusettsMember |  |
Building Improvements | 3,762,013 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NorthBeacon140LPResidentialUnitsBostonMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 1,818,227 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NorthBeacon140LPResidentialUnitsBostonMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 936,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NorthBeacon140LPResidentialUnitsBostonMassachusettsMember |  |
Building Improvements | 5,580,240 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NorthBeacon140LPResidentialUnitsBostonMassachusettsMember |  |
Totals | 6,516,240 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NorthBeacon140LPResidentialUnitsBostonMassachusettsMember |  |
Accumulated Depreciation | 3,476,883 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_NorthBeacon140LPResidentialUnitsBostonMassachusettsMember |  |
Olde English Apartments L.P. Residential Apartments Lowell, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 2,248,758 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_OldeEnglishApartmentsLPResidentialApartmentsLowellMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 1,354,946 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_OldeEnglishApartmentsLPResidentialApartmentsLowellMassachusettsMember |  |
Encumbrances (First Mortgages) | 3,080,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_OldeEnglishApartmentsLPResidentialApartmentsLowellMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 46,181 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_OldeEnglishApartmentsLPResidentialApartmentsLowellMassachusettsMember |  |
Building Improvements | 878,323 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_OldeEnglishApartmentsLPResidentialApartmentsLowellMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 1,324,254 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_OldeEnglishApartmentsLPResidentialApartmentsLowellMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 46,181 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_OldeEnglishApartmentsLPResidentialApartmentsLowellMassachusettsMember |  |
Building Improvements | 2,202,577 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_OldeEnglishApartmentsLPResidentialApartmentsLowellMassachusettsMember |  |
Totals | 2,248,758 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_OldeEnglishApartmentsLPResidentialApartmentsLowellMassachusettsMember |  |
Accumulated Depreciation | 1,354,946 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_OldeEnglishApartmentsLPResidentialApartmentsLowellMassachusettsMember |  |
Redwood Hills L.P. Residential Units Worcester, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 8,906,659 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RedwoodHillsLPResidentialUnitsWorcesterMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 4,402,390 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RedwoodHillsLPResidentialUnitsWorcesterMassachusettsMember |  |
Encumbrances (First Mortgages) | 6,743,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RedwoodHillsLPResidentialUnitsWorcesterMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 1,200,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RedwoodHillsLPResidentialUnitsWorcesterMassachusettsMember |  |
Building Improvements | 4,810,604 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RedwoodHillsLPResidentialUnitsWorcesterMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 2,896,055 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RedwoodHillsLPResidentialUnitsWorcesterMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 1,200,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RedwoodHillsLPResidentialUnitsWorcesterMassachusettsMember |  |
Building Improvements | 7,706,659 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RedwoodHillsLPResidentialUnitsWorcesterMassachusettsMember |  |
Totals | 8,906,659 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RedwoodHillsLPResidentialUnitsWorcesterMassachusettsMember |  |
Accumulated Depreciation | 4,402,390 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RedwoodHillsLPResidentialUnitsWorcesterMassachusettsMember |  |
River Drive L.P. Residential Apartments Danvers, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 1,339,247 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RiverDriveLPResidentialApartmentsDanversMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 919,183 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RiverDriveLPResidentialApartmentsDanversMassachusettsMember |  |
Encumbrances (First Mortgages) | 3,465,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RiverDriveLPResidentialApartmentsDanversMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 72,525 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RiverDriveLPResidentialApartmentsDanversMassachusettsMember |  |
Building Improvements | 587,777 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RiverDriveLPResidentialApartmentsDanversMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 678,945 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RiverDriveLPResidentialApartmentsDanversMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 72,525 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RiverDriveLPResidentialApartmentsDanversMassachusettsMember |  |
Building Improvements | 1,266,722 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RiverDriveLPResidentialApartmentsDanversMassachusettsMember |  |
Totals | 1,339,247 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RiverDriveLPResidentialApartmentsDanversMassachusettsMember |  |
Accumulated Depreciation | 919,183 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_RiverDriveLPResidentialApartmentsDanversMassachusettsMember |  |
Riverside Apartments Condominium Units Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 235,859 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CondominiumUnitsRiversideResidentialUnitsMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 202,257 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CondominiumUnitsRiversideResidentialUnitsMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 23,346 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CondominiumUnitsRiversideResidentialUnitsMassachusettsMember |  |
Building Improvements | 190,807 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CondominiumUnitsRiversideResidentialUnitsMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 21,706 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CondominiumUnitsRiversideResidentialUnitsMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 23,346 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CondominiumUnitsRiversideResidentialUnitsMassachusettsMember |  |
Building Improvements | 212,513 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CondominiumUnitsRiversideResidentialUnitsMassachusettsMember |  |
Totals | 235,859 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CondominiumUnitsRiversideResidentialUnitsMassachusettsMember |  |
Accumulated Depreciation | 202,257 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CondominiumUnitsRiversideResidentialUnitsMassachusettsMember |  |
School St Assoc LLC Residential Apartments Framingham, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 21,851,711 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_SchoolStAssocLLCResidentialApartmentsFraminghamMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 7,285,429 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_SchoolStAssocLLCResidentialApartmentsFraminghamMassachusettsMember |  |
Encumbrances (First Mortgages) | 15,000,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_SchoolStAssocLLCResidentialApartmentsFraminghamMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 4,686,728 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_SchoolStAssocLLCResidentialApartmentsFraminghamMassachusettsMember |  |
Building Improvements | 18,746,911 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_SchoolStAssocLLCResidentialApartmentsFraminghamMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | (1,581,928)us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_SchoolStAssocLLCResidentialApartmentsFraminghamMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 4,686,728 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_SchoolStAssocLLCResidentialApartmentsFraminghamMassachusettsMember |  |
Building Improvements | 17,164,983 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_SchoolStAssocLLCResidentialApartmentsFraminghamMassachusettsMember |  |
Totals | 21,851,711 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_SchoolStAssocLLCResidentialApartmentsFraminghamMassachusettsMember |  |
Accumulated Depreciation | 7,285,429 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_SchoolStAssocLLCResidentialApartmentsFraminghamMassachusettsMember |  |
WRF Associates LLC Strip Mall Framingham, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 8,242,069 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_StaplesPlazaStripMallFraminghamMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 2,568,515 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_StaplesPlazaStripMallFraminghamMassachusettsMember |  |
Encumbrances (First Mortgages) | 6,000,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_StaplesPlazaStripMallFraminghamMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 3,280,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_StaplesPlazaStripMallFraminghamMassachusettsMember |  |
Building Improvements | 4,920,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_StaplesPlazaStripMallFraminghamMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 42,069 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_StaplesPlazaStripMallFraminghamMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 3,280,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_StaplesPlazaStripMallFraminghamMassachusettsMember |  |
Building Improvements | 4,962,069 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_StaplesPlazaStripMallFraminghamMassachusettsMember |  |
Totals | 8,242,069 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_StaplesPlazaStripMallFraminghamMassachusettsMember |  |
Accumulated Depreciation | 2,568,515 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_StaplesPlazaStripMallFraminghamMassachusettsMember |  |
WCB Associates LLC Residential Apartments Brockton, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 10,074,708 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WCBAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 4,992,376 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WCBAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Encumbrances (First Mortgages) | 7,000,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WCBAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 1,335,000 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WCBAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Building Improvements | 7,565,501 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WCBAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 1,174,207 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WCBAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 1,335,000 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WCBAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Building Improvements | 8,739,708 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WCBAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Totals | 10,074,708 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WCBAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Accumulated Depreciation | 4,992,376 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WCBAssociatesLLCResidentialApartmentsBrocktonMassachusettsMember |  |
Courtyard At Westgate Residential Units Burlington Massachusetts Member |  |  |
Deduct |  |  |
Balance, Ending | 4,765,224 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CourtyardAtWestgateResidentialUnitsBurlingtonMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 1,815,417 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CourtyardAtWestgateResidentialUnitsBurlingtonMassachusettsMember |  |
Encumbrances (First Mortgages) | 2,500,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CourtyardAtWestgateResidentialUnitsBurlingtonMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 44,965 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CourtyardAtWestgateResidentialUnitsBurlingtonMassachusettsMember |  |
Building Improvements | 4,478,687 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CourtyardAtWestgateResidentialUnitsBurlingtonMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 241,572 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CourtyardAtWestgateResidentialUnitsBurlingtonMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 44,965 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CourtyardAtWestgateResidentialUnitsBurlingtonMassachusettsMember |  |
Building Improvements | 4,720,259 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CourtyardAtWestgateResidentialUnitsBurlingtonMassachusettsMember |  |
Totals | 4,765,224 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CourtyardAtWestgateResidentialUnitsBurlingtonMassachusettsMember |  |
Accumulated Depreciation | 1,815,417 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_CourtyardAtWestgateResidentialUnitsBurlingtonMassachusettsMember |  |
Westgate Apartments LLC Residential Apartments Woburn, Massachusetts |  |  |
Deduct |  |  |
Balance, Ending | 10,158,127 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WestgateApartmentsLLCResidentialApartmentsWoburnMassachusettsMember |  |
Deduct: |  |  |
Balance, Ending | 6,186,013 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WestgateApartmentsLLCResidentialApartmentsWoburnMassachusettsMember |  |
Encumbrances (First Mortgages) | 15,700,000 us-gaap_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WestgateApartmentsLLCResidentialApartmentsWoburnMassachusettsMember |  |
Initial Cost to Partnerships |  |  |
Land | 461,300 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WestgateApartmentsLLCResidentialApartmentsWoburnMassachusettsMember |  |
Building Improvements | 2,424,636 us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WestgateApartmentsLLCResidentialApartmentsWoburnMassachusettsMember |  |
Cost Capitalized Subsequent to Acquisition |  |  |
Improvements | 7,316,384 us-gaap_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WestgateApartmentsLLCResidentialApartmentsWoburnMassachusettsMember |  |
Gross Amount at Which Carried at Close of Period |  |  |
Land | 417,107 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WestgateApartmentsLLCResidentialApartmentsWoburnMassachusettsMember |  |
Building Improvements | 9,741,020 us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WestgateApartmentsLLCResidentialApartmentsWoburnMassachusettsMember |  |
Totals | 10,158,127 us-gaap_RealEstateGrossAtCarryingValue / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WestgateApartmentsLLCResidentialApartmentsWoburnMassachusettsMember |  |
Accumulated Depreciation | $ 6,186,013 us-gaap_RealEstateAccumulatedDepreciation / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_WestgateApartmentsLLCResidentialApartmentsWoburnMassachusettsMember |  |

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