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Investments in affiliates and joint ventures - Narrative (Details) - Variable Interest Entity, Not Primary Beneficiary | 12 Months Ended
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Dec. 31, 2018
Dene North Site Services Partnership |
Variable Interest Entity [Line Items] |
NL Partnership Interest in VIEs | 49.00%
Mikisew North American Limited Partnership |
Variable Interest Entity [Line Items] |
NL Partnership Interest in VIEs | 49.00%

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- 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
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- Definition Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 810 -SubTopic 10 -Section 50 -Paragraph 5A -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=108788376&loc=SL6759159-111685 + Details
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- Details
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- Details
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