Represents the increase in aggregate indebtedness of the subsidiaries and joint ventures.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the ratio of consolidated adjusted earnings before interest, taxes, depreciation and amortization to interest expense, which is necessary to be maintained under the terms of the senior credit facilities' covenants.

+ References

No definition available.

+ Details

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Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the ratio of consolidated total debt to consolidated adjusted earnings before, interest, taxes, depreciation and amortization allowed under the terms of the senior credit facilities' covenants.

+ References

No definition available.

+ Details

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Namespace Prefix:	nen_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represent the total cost of the unused line of credit commitment fee.

+ References

No definition available.

+ Details

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

- Definition

Represents the percentage points added to the reference rate to compute the variable rate which is used in calculation of base rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	nen_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the reference rate for the variable rate used in calculation of base rate of the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	nen_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the percentage of pledged interests of the Partnership's ownership interest.

+ References

No definition available.

+ Details

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Namespace Prefix:	nen_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the ratio of net operating income to total indebtedness.

+ References

No definition available.

+ Details

Name:	nen_NetOperatingIncomeToTotalIndebtednessRatio
Namespace Prefix:	nen_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the level of tangible net worth required to maintain.

+ References

No definition available.

+ Details

Name:	nen_TangibleNetWorth
Namespace Prefix:	nen_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the fee that accompanies borrowing money under the debt instrument.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

No definition available.

+ Details

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

- Details

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- Details

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Name:	us-gaap_VariableRateAxis=us-gaap_PrimeRateMember
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Data Type:	na
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- Details

Name:	us-gaap_VariableRateAxis=nen_Nen_FederalFundsRateMember
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Data Type:	na
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- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
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- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_MortgagesMember
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MORTGAGE NOTES PAYABLE AND LINE OF CREDIT (Line of Credit) (Details)				1 Months Ended	9 Months Ended	12 Months Ended
	Jan. 07, 2016	Sep. 30, 2015	Jul. 31, 2014 USD ($) item	Aug. 31, 2014	Sep. 30, 2016 USD ($)	Dec. 31, 2005 item	Dec. 31, 2015 USD ($)	Mar. 07, 2005 item
Line of Credit
Credit line balance							$ 25,000,000
Line Of Credit Facility Unused Capacity Commitment Fee					$ 37,000
Hamilton Essex 81
Line of Credit
Number of properties in which borrowing amount collateralized \| item								1
Line of Credit
Line of Credit
Maximum borrowings			$ 25,000,000
Term of debt			3 years
Amount of refinancing costs			$ 125,000
Credit line balance					0
Number of properties in which borrowing amount collateralized \| item			23
Base Rate \| Line of Credit
Line of Credit
Reference rate used in calculation of Base Rate			base
Prime Rate [Member] \| Line of Credit
Line of Credit
Reference rate used in calculation of Base Rate			Prime
Federal Funds Rate \| Line of Credit
Line of Credit
Reference rate used in calculation of Base Rate			Federal Funds
Basis of effective interest rate used in calculation of Base Rate (as a percent)			0.50%
LIBOR \| Residences at CaptainParkers LLC Residential Apartments Lexington, Massachusetts
Line of Credit
Margin over basis of interest rate (as a percent)	201.00%
LIBOR \| Line of Credit
Line of Credit
Reference rate used in calculation of Base Rate			one month LIBOR
Basis of effective interest rate used in calculation of Base Rate (as a percent)			1.00%
Minimum
Line of Credit
Tangible net worth					$ 150,000,000
Ratio of net operating income to total indebtedness					9.50%
Debt service coverage ratio					1.6
Minimum \| Line of Credit
Line of Credit
Pledged interests of the Partnership's ownership interest (as a percent)			49.00%
Commitment fee for unused amount (as a percent)			0.15%
Minimum \| Base Rate \| Line of Credit
Line of Credit
Margin over basis of interest rate (as a percent)			2.50%
Maximum
Line of Credit
Leverage ratio					65.00%
Aggregate increase in indebtedness					$ 15,000,000
Maximum \| Line of Credit
Line of Credit
Pledged interests of the Partnership's ownership interest (as a percent)			100.00%
Commitment fee for unused amount (as a percent)			0.20%
Mortgages payable \| Hamilton Essex 81
Line of Credit
Term of debt		10 years
Mortgages payable \| Hamilton on Main Apartments, LLC
Line of Credit
Term of debt				10 years		10 years
Number of properties in which borrowing amount collateralized \| item						3
Mortgages payable \| LIBOR \| Hamilton Essex 81
Line of Credit
Margin over basis of interest rate (as a percent)		2.18%