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v3.20.2

SUBSEQUENT EVENTS (Details) - shares |  | 1 Months Ended | 2 Months Ended | 3 Months Ended | 6 Months Ended | 132 Months Ended
--- | --- | --- | --- | --- | --- | ---
Aug. 31, 2007 | Sep. 30, 2007 | Aug. 31, 2020 | Dec. 31, 2007 | Jun. 30, 2019 | Dec. 31, 2018
Subsequent events |  |  |  |  |  |
Number of depository receipts repurchased | 1,428,437 | 1,428,437 |  | 1,428,437 | 1,428,437 | 1,428,437
Subsequent event |  |  |  |  |  |
Subsequent events |  |  |  |  |  |
Number of depository receipts repurchased |  |  | 0 |  |  |

X
- Definition Represents the number of depository receipts repurchased under the equity repurchase program. + References No definition available. + Details
Name: | nen_PartnersCapitalAccountDepositoryReceiptsTreasury
Namespace Prefix: | nen_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |