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SUBSEQUENT EVENTS (Details) (USD $)	0 Months Ended	12 Months Ended			76 Months Ended	88 Months Ended		1 Months Ended	2 Months Ended
	Mar. 10, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2014	Feb. 28, 2014	Mar. 10, 2015	Mar. 06, 2008	Jan. 30, 2008	Jan. 15, 2008	Aug. 20, 2007
Subsequent events
Repurchase of depository receipts		44,025nen_PartnersCapitalAccountDepositoryReceiptsTreasury	22,964nen_PartnersCapitalAccountDepositoryReceiptsTreasury		1,286,916nen_PartnersCapitalAccountDepositoryReceiptsTreasury		1,286,916nen_PartnersCapitalAccountDepositoryReceiptsTreasury
Repurchase price of depository receipts		$ 47.90nen_PartnersCapitalAccountDepositoryReceiptsTreasuryAverageRepurchasePricePerDepositoryReceipt	$ 37.80nen_PartnersCapitalAccountDepositoryReceiptsTreasuryAverageRepurchasePricePerDepositoryReceipt			$ 25.65nen_PartnersCapitalAccountDepositoryReceiptsTreasuryAverageRepurchasePricePerDepositoryReceipt
Repurchase price of units		$ 1,437nen_PartnersCapitalAccountUnitsTreasuryAverageRepurchasePricePerUnit	$ 1,134nen_PartnersCapitalAccountUnitsTreasuryAverageRepurchasePricePerUnit
Repurchase of units		1,834us-gaap_PartnersCapitalAccountUnitsTreasury	957us-gaap_PartnersCapitalAccountUnitsTreasury	1,040us-gaap_PartnersCapitalAccountUnitsTreasury
Total cost of repurchase		$ 2,685,583us-gaap_PartnersCapitalAccountTreasuryUnitsPurchases	$ 1,094,609us-gaap_PartnersCapitalAccountTreasuryUnitsPurchases	$ 906,214us-gaap_PartnersCapitalAccountTreasuryUnitsPurchases		$ 35,167,000us-gaap_PartnersCapitalAccountTreasuryUnitsPurchases
Gain on the sale			3,678,839us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax
Depository receipts authorized to be repurchased	2,000,000nen_PartnersCapitalAccountDepositoryReceiptsTreasuryReceiptsAuthorizedToBeRepurchased								2,000,000nen_PartnersCapitalAccountDepositoryReceiptsTreasuryReceiptsAuthorizedToBeRepurchased	1,500,000nen_PartnersCapitalAccountDepositoryReceiptsTreasuryReceiptsAuthorizedToBeRepurchased	900,000nen_PartnersCapitalAccountDepositoryReceiptsTreasuryReceiptsAuthorizedToBeRepurchased	600,000nen_PartnersCapitalAccountDepositoryReceiptsTreasuryReceiptsAuthorizedToBeRepurchased	300,000nen_PartnersCapitalAccountDepositoryReceiptsTreasuryReceiptsAuthorizedToBeRepurchased
Repurchase program extension (In years)	5 years
Hamilton Bay Apartments
Subsequent events
Gain on the sale		0us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax / us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis = nen_HamiltonBayApartmentsLLCMember
Mortgages payable | Linhart L.P. Residential/Commercial Newton, Massachusetts
Subsequent events
Amount of mortgage paid off								1,926,000us-gaap_RepaymentsOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_LinhartLPResidentialCommercialNewtonMassachusettsMember
Mortgages payable | Hamilton Linewt LLC Commercial-1031Exchange Newton, Massachusetts
Subsequent events
Amount of mortgage paid off								1,466,000us-gaap_RepaymentsOfDebt / us-gaap_LongtermDebtTypeAxis = us-gaap_MortgagesMember / us-gaap_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis = nen_HamiltonLinewtLLCCommercial1031ExchangeNewtonMassachusettsMember
Subsequent event
Subsequent events
Repurchase of depository receipts									19,415nen_PartnersCapitalAccountDepositoryReceiptsTreasury / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Repurchase price of depository receipts									$ 50.00nen_PartnersCapitalAccountDepositoryReceiptsTreasuryAverageRepurchasePricePerDepositoryReceipt / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Repurchase price of units									$ 1,500.00nen_PartnersCapitalAccountUnitsTreasuryAverageRepurchasePricePerUnit / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Repurchase of depository receipts									$ 975,731nen_PartnersCapitalAccountDepositoryReceiptsTreasuryRepurchased / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember

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Amount of gain (loss), after tax expense or benefit and not previously recognized, resulting from the sale of a business component.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 205

-SubTopic 20

-Section 45

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