Represents the capacity of real estate property.

No definition available.

Name:	nen_CapacityOfRealEstateProperty
Namespace Prefix:	nen_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	num:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The number of units in a real estate property owned as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfUnitsInRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

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.

+ References

No definition available.

+ Details

Name:	us-gaap_RealEstatePropertiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_RealEstatePropertiesAxis=us-gaap_WhollyOwnedPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=nen_ResidentialAndMixedUseRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=us-gaap_ResidentialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=nen_ResidentialRetailAndOfficeBuildingMixedUseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=nen_CondominiumRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RealEstatePropertiesAxis=us-gaap_PartiallyOwnedPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=nen_CarParkingLotRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=nen_InvestmentPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
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SIGNIFICANT ACCOUNTING POLICIES (Business) (Details)	Dec. 31, 2015 ft² property item	Dec. 31, 2014 item	Dec. 31, 2013 item
Wholly owned properties
Line of Business
Number of properties \| property	25
Wholly owned properties \| Residential and mixed-use properties
Line of Business
Number of properties \| property	21
Number of units	2,506
Wholly owned properties \| Residential buildings
Line of Business
Number of properties \| property	17
Wholly owned properties \| Mixed use residential, retail and office buildings
Line of Business
Number of properties \| property	4
Wholly owned properties \| Commercial
Line of Business
Number of properties \| property	3
Area of property (in square feet) \| ft²	108,043
Wholly owned properties \| Condominium
Line of Business
Number of properties \| property	1
Number of units	19
Partially owned properties \| Residential and mixed-use properties
Line of Business
Number of properties	9
Number of units	788
Partially owned properties \| Commercial
Line of Business
Area of property (in square feet) \| ft²	12,500
Partially owned properties \| Car parking lot
Line of Business
Capacity of real estate property (in cars per lot)	50
Investment Properties
Line of Business
Number of units	1,033	1,033	1,033
Investment Properties \| Minimum
Line of Business
Ownership interest (as a percent)	40.00%
Investment Properties \| Maximum
Line of Business
Ownership interest (as a percent)	50.00%
Investment Properties \| Residential buildings
Line of Business
Number of units	1,030	1,030	1,030
Investment Properties \| Commercial
Line of Business
Number of units	3	3	3
Investment Properties \| Partially owned properties \| Residential and mixed-use properties
Line of Business
Number of properties	9
Investment Properties \| Partially owned properties \| Residential and mixed-use properties \| Minimum
Line of Business
Ownership interest (as a percent)	40.00%
Investment Properties \| Partially owned properties \| Residential and mixed-use properties \| Maximum
Line of Business
Ownership interest (as a percent)	50.00%