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

The number of real estate properties owned after the balance sheet date but prior to the reporting date.

+ References

No definition available.

+ Details

Name:	nen_NumberOfRealEstatePropertiesAfterBalanceSheetDate
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://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

+ 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:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=us-gaap_ResidentialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=nen_ResidentialAndMixedUseRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=nen_ResidentialRetailAndOfficeBuildingMixedUseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_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:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=nen_CarParkingLotRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=nen_InvestmentPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
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SIGNIFICANT ACCOUNTING POLICIES (Business) (Details)	Dec. 31, 2019 ft² property item	Dec. 31, 2018 item	Dec. 31, 2017 item
Line of Business
Number of units	913	913	913
Residential buildings
Line of Business
Number of units	910	910	910
Commercial
Line of Business
Number of units	3	3	3
Wholly owned properties
Line of Business
Number of Real Estate Properties \| property	29
Wholly owned properties \| Residential and mixed-use properties
Line of Business
Number of Real Estate Properties \| property	25
Number of units	2,892
Wholly owned properties \| Residential buildings
Line of Business
Number of Real Estate Properties \| property	21
Wholly owned properties \| Mixed use residential, retail and office buildings
Line of Business
Number of Real Estate Properties \| property	4
Wholly owned properties \| Commercial
Line of Business
Number of Real Estate Properties \| property	3
Area of property (in square feet) \| ft²	108,043
Wholly owned properties \| Condominium
Line of Business
Number of Real Estate Properties \| property	1
Number of units	19
Partially owned properties \| Residential and mixed-use properties
Line of Business
Number of Real Estate Properties	7
Number of properties after balance sheet date	688
Number of units	688
Partially owned properties \| Residential and mixed-use properties \| Minimum
Line of Business
Ownership interest (as a percent)	40.00%
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 \| 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 \| Partially owned properties \| Residential and mixed-use properties
Line of Business
Number of Real Estate Properties	7
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%