Name:	dei_EntityListingDepositoryReceiptRatio
Namespace Prefix:	dei_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

Represents the number of depository receipts and partnership units authorized to be repurchased under the equity repurchase program.

No definition available.

Name:	nen_PartnersCapitalAccountDepositoryReceiptsAndPartnershipUnitsAuthorizedToBeRepurchased
Namespace Prefix:	nen_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the number of depository receipts repurchased under the equity repurchase program.

No definition available.

Name:	nen_PartnersCapitalAccountDepositoryReceiptsTreasury
Namespace Prefix:	nen_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Represents the average price at which depository receipts are repurchased under the equity repurchase program.

No definition available.

Name:	nen_PartnersCapitalAccountDepositoryReceiptsTreasuryAverageRepurchasePricePerDepositoryReceipt
Namespace Prefix:	nen_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	duration

Represents the number of depository receipts authorized to be repurchased under the equity repurchase program.

No definition available.

Name:	nen_PartnersCapitalAccountDepositoryReceiptsTreasuryReceiptsAuthorizedToBeRepurchased
Namespace Prefix:	nen_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Represents the fixed distribution percentages of the holders of units based on which the entity is required to purchase the proportionate number of specific units with every purchase of depository receipts.

No definition available.

Name:	nen_PartnersCapitalAccountFixedDistributionPercentageOfHoldersOfUnits
Namespace Prefix:	nen_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Represents the period over which the entity is permitted to purchase its depository receipts.

No definition available.

Name:	nen_PartnersCapitalAccountPeriodForRepurchaseOfDepositoryReceipts
Namespace Prefix:	nen_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the number of treasury units outstanding as on the balance sheet date.

No definition available.

Name:	nen_PartnersCapitalAccountTreasuryUnitsIssued
Namespace Prefix:	nen_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Value of units that were previously issued and have been repurchased during the year.

No definition available.

Name:	nen_PartnersCapitalAccountTreasuryUnitsPurchasesIncludingCommission
Namespace Prefix:	nen_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the average price at which units are repurchased under the equity repurchase program.

No definition available.

Name:	nen_PartnersCapitalAccountUnitsTreasuryAverageRepurchasePricePerUnit
Namespace Prefix:	nen_
Data Type:	srt-types:perUnitItemType
Balance Type:	na
Period Type:	duration

Value of units that were previously issued and have been repurchased during the year.

No definition available.

Name:	us-gaap_PartnersCapitalAccountTreasuryUnitsPurchases
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Units that were previously issued and have been repurchased during the year.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 5
-Subparagraph (SAB Topic 4.F)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-5

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Data Type:	xbrli:sharesItemType
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Period Type:	duration

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Namespace Prefix:
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Name:	srt_StatementScenarioAxis=nen_PriceInExcessOfHighestAmountOfDepositaryReceiptPaidDividedByOneThirtiethPerPartnershipUnitMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_PartnerTypeOfPartnersCapitalAccountAxis=nen_LimitedClassAMember
Namespace Prefix:
Data Type:	na
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Name:	us-gaap_PartnerTypeOfPartnersCapitalAccountAxis=nen_LimitedClassBMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	us-gaap_PartnerTypeOfPartnersCapitalAccountAxis=us-gaap_GeneralPartnerMember
Namespace Prefix:
Data Type:	na
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