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Financial instruments - Derivatives (Details) - CAD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019
Disclosure of detailed information about financial instruments [line items] |  |
Net | $ 40,872 | $ (2,020)
Gain (loss) | 36,577 | 32,269
Current portion of other liabilities [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Net | (1,658) | (7,505)
Other liabilities [Member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Net | (3,075) | (5,019)
Current portion of long-term receivables, investments and other [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Net | 16,466 | 4,144
Long-term receivables, investments and other [Member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Net | 29,139 | 6,360
Foreign currency contracts [Member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Net | 40,872 | (4,333)
Gain (loss) | 30,600 | 31,863
Interest rate swap contracts [member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Net | 0 | 2,313
Gain (loss) | 5,977 | 2,068
Uranium contracts [Member] |  |
Disclosure of detailed information about financial instruments [line items] |  |
Gain (loss) | $ 0 | $ (1,662)

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- Definition The gains (losses) resulting from change in the fair value of derivatives recognised in profit or loss. [Refer: Derivatives [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 1 -IssueDate 2020-01-01 -Paragraph 85 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2020-en-r&anchor=para_85&doctype=Standard -URIDate 2020-01-01 + Details
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