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://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=nen_ResidentialAndMixedUseRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- 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:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=nen_CondominiumRealEstateMember
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_ResidentialRetailAndOfficeBuildingMixedUseMember
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_RangeAxis=srt_MaximumMember
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:
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SIGNIFICANT ACCOUNTING POLICIES (Business) (Details)	Jun. 30, 2019 ft² property item	Jun. 30, 2018 property
Line of Business
Number of units \| property		913
Residential and mixed-use properties
Line of Business
Number of Real Estate Properties	23
Number of units	2,711
Residential buildings
Line of Business
Number of units \| property		910
Commercial
Line of Business
Number of units \| property		3
Condominium
Line of Business
Number of units	19
Wholly owned properties
Line of Business
Number of Real Estate Properties	27
Wholly owned properties \| Residential buildings
Line of Business
Number of Real Estate Properties	19
Number of units	2,711
Wholly owned properties \| Mixed use residential, retail and office buildings
Line of Business
Number of Real Estate Properties	4
Wholly owned properties \| Commercial
Line of Business
Number of Real Estate Properties	3
Area of property (in square feet) \| ft²	108,043
Wholly owned properties \| Condominium
Line of Business
Number of Real Estate Properties	1
Number of units	19
Partially owned properties \| Residential and mixed-use properties
Line of Business
Number of Real Estate Properties	8
Number of units	688
Area of property (in square feet) \| ft²	12,500
Partially owned properties \| Residential and mixed-use properties \| Minimum
Line of Business
Ownership interest (as a percent)	40.00%
Partially owned properties \| Residential and mixed-use properties \| Maximum
Line of Business
Ownership interest (as a percent)	50.00%
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 \| property	913
Investment Properties \| Residential buildings
Line of Business
Number of units \| property	910
Investment Properties \| Commercial
Line of Business
Number of units \| property	3
Investment Properties \| Partially owned properties \| Residential and mixed-use properties
Line of Business
Number of units \| property	688