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SEGMENTED INFORMATION (Details Textual) - USD ($) $ in Millions | 1 Months Ended | 12 Months Ended
--- | --- | ---
Feb. 28, 2017 | Dec. 31, 2017 | Dec. 31, 2016
Gains on Disposal of El Morro Stream | $ 33.0 | $ 33.0 | $ 0.0
Major Customer [Member] |  |  |
Percentage of entity's revenue |  | 79.00% | 71.00%

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- Definition The percentage of the entity's revenue. [Refer: Revenue] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IFRS -Number 8 -IssueDate 2017-01-01 -Paragraph 34 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=8&date=2017-03-01&anchor=para_34&doctype=Standard -URIDate 2017-03-09 + Details
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Namespace Prefix: | ifrs-full_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition The gain on the disposal of El Morro stream. + References No definition available. + Details
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Namespace Prefix: | ngd_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Details
Name: | ngd_MajorCustomerAxis=ngd_MajorCustomerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |