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Other long-term liabilities and deferred credits - Changes in Environmental Remediation Obligation (Details) - CAD CAD in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016
Accrual for Environmental Loss Contingencies [Roll Forward] |  |
Opening Balance | CAD 63,378 | CAD 71,529
Remediation activities | (2,026) | (1,389)
Accretion | 1,447 | 2,464
Changes in cash flow estimates | 2,135 | 2,088
Revision in assumptions | 7,686 | (9,101)
Foreign exchange rate adjustment | (4,473) | (2,213)
Closing Balance | CAD 68,147 | CAD 63,378

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- Definition Accrual for Environmental Loss Contingencies, Increase (Decrease) for Revision in Assumptions + References No definition available. + Details
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- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82911808&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 30 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6393242&loc=d3e13207-110859 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6395460&loc=d3e13647-108346 + Details
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- Definition Amount of foreign currency translation gain (loss) which decreases (increases) the accrual for environmental loss contingencies. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.Y.Q2) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 + Details
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- Definition Amount of expense (reversal of expense) which increases (decreases) the accrual for environmental loss contingencies from revisions in estimates to existing obligations. Excludes changes related to business acquisitions, divestitures, or currency movement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.Y.Q2) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 + Details
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- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
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