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:	dtr-types: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 https://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types: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:	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=nen_ResidentialRetailAndOfficeBuildingMixedUseMember
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_PartiallyOwnedPropertiesMember
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_LimitedPartnershipsMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=nen_NewEnglandRealtyAssociatesLimitedPartnership40PercentOwnershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=nen_NewEnglandRealtyAssociatesLimitedPartnership50PercentOwnershipMember
Namespace Prefix:
Data Type:	na
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SIGNIFICANT ACCOUNTING POLICIES (Business) (Details)	Mar. 31, 2023 property	Mar. 31, 2023 item	Mar. 31, 2023 ft²	Mar. 31, 2023	Mar. 31, 2022
Wholly owned properties
Line of Business
Number of properties	30
Wholly owned properties \| Residential and mixed-use properties
Line of Business
Number of properties	25
Number of units \| item		2,892
Wholly owned properties \| Residential buildings
Line of Business
Number of properties	21
Wholly owned properties \| Mixed use residential, retail and office buildings
Line of Business
Number of properties	4
Wholly owned properties \| Commercial
Line of Business
Number of properties	5
Area of property (in square feet) \| ft²			128,096
Wholly owned properties \| Condominium
Line of Business
Number of properties	1
Number of units \| item		19
Partially owned properties \| Residential and mixed-use properties
Line of Business
Number of units	688	688
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) \| item		50
Limited Partnerships \| Partially owned properties \| Residential and mixed-use properties
Line of Business
Number of properties \| item		7
NERA 40%
Line of Business
Ownership interest (as a percent)				40.00%	40.00%
NERA 50%
Line of Business
Ownership interest (as a percent)				50.00%	50.00%