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Risk Management Activities - Impact of hedged items designated in hedging relationships on OCI and net earnings (Details) - CAD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Disclosure of detailed information about hedging instruments [line items] |  |  |
Gains (losses) on cash flow hedges, before tax | $ (255) | $ 28 | $ 77
Losses recognized in other comprehensive earnings | (8) | (141) | (53)
Gain (loss) on hedge ineffectiveness recognised in profit or loss | 0 | 0 | 0
Commodity contracts |  |  |
Disclosure of detailed information about hedging instruments [line items] |  |  |
Gains (losses) on cash flow hedges, before tax | (268) | 41 | 77
Commodity contracts | Revenue |  |  |
Disclosure of detailed information about hedging instruments [line items] |  |  |
Losses recognized in other comprehensive earnings | (13) | (137) | (59)
Gain (loss) on hedge ineffectiveness recognised in profit or loss | 0 | 0 | 0
Foreign exchange forwards on project hedges |  |  |
Disclosure of detailed information about hedging instruments [line items] |  |  |
Gains (losses) on cash flow hedges, before tax | 0 | (1) |
Foreign exchange forwards on project hedges | Property, plant and equipment |  |  |
Disclosure of detailed information about hedging instruments [line items] |  |  |
Losses recognized in other comprehensive earnings | 1 | 0 |
Gain (loss) on hedge ineffectiveness recognised in profit or loss | 0 | 0 |
Forward starting interest rate swaps |  |  |
Disclosure of detailed information about hedging instruments [line items] |  |  |
Gains (losses) on cash flow hedges, before tax | 13 | (12) | 0
Forward starting interest rate swaps | Interest expense |  |  |
Disclosure of detailed information about hedging instruments [line items] |  |  |
Losses recognized in other comprehensive earnings | 4 | (4) | 6
Gain (loss) on hedge ineffectiveness recognised in profit or loss | $ 0 | $ 0 | $ 0

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- Definition The gain (loss) recognised in other comprehensive income on hedge ineffectiveness. [Refer: Gain (loss) on hedge ineffectiveness] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2021-01-01 -Paragraph 24C -Subparagraph a -Clause i -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2021-en-r&anchor=para_24C_a_i&doctype=Standard -URIDate 2021-03-24 + Details
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- Definition The gain (loss) recognised in profit or loss on hedge ineffectiveness. [Refer: Gain (loss) on hedge ineffectiveness] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2021-01-01 -Paragraph 24C -Subparagraph a -Clause i -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2021-en-r&anchor=para_24C_a_i&doctype=Standard -URIDate 2021-03-24 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name IFRS -Number 7 -IssueDate 2021-01-01 -Paragraph 24C -Subparagraph b -Clause ii -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2021-en-r&anchor=para_24C_b_ii&doctype=Standard -URIDate 2021-03-24 + Details
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- Definition The gains (losses) recognised in other comprehensive income on cash flow hedges, before tax, before reclassification adjustments. [Refer: Cash flow hedges [member]] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 1 -IssueDate 2021-01-01 -Paragraph 91 -Subparagraph b -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=1&code=ifrs-tx-2021-en-r&anchor=para_91_b&doctype=Standard -URIDate 2021-03-24 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Note Expiry date 2023-01-01 -Name IFRS -Number 7 -IssueDate 2021-01-01 -Paragraph 23 -Subparagraph c -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=7&code=ifrs-tx-2017-en-b&anchor=para_23_c&doctype=Standard&book=b -URIDate 2021-03-24 + Details
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