Name:	nen_InvestmentsInNumberOfLimitedPartnershipsAndLimitedLiabilityCompanies
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Number of employees, excluding President, having ownership interest in the investment properties.

No definition available.

Name:	nen_NumberOfEmployeesHavingOwnershipInterest
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Data Type:	xbrli:integerItemType
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Represents the number of partnerships which are investing in commercial properties.

No definition available.

Name:	nen_NumberOfPartnershipsInvestingInCommercialProperties
Namespace Prefix:	nen_
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The percentage of ownership of common stock or equity participation in the investee by related party.

No definition available.

Name:	nen_RelatedPartyOwnershipInterest
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Data Type:	num:percentItemType
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Period Type:	instant

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

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

No definition available.

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Name:	srt_RangeAxis=srt_MinimumMember
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