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Decommissioning and Other Provisions - Change in Decommissioning and Other Provision Balances (Details) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Reconciliation of changes in other provisions [abstract] |  |
Balance | $ 456 | $ 470
Liabilities incurred | 14 | 22
Liabilities settled | (43) | (41)
Accretion | (23) | 24
Acquisition of liabilities | 19 | 8
Revisions in estimated cash flows | 103 | 5
Revisions in discount rates | 16 | (37)
Reversals | (1) | (5)
Change in foreign exchange rates | (7) | 10
Liabilities disposed | (32) |
Balance | 546 | 456
Decommissioning and restoration |  |
Reconciliation of changes in other provisions [abstract] |  |
Balance | 407 | 437
Liabilities incurred | 7 | 5
Liabilities settled | (34) | (31)
Accretion | (23) | 24
Acquisition of liabilities | 16 | 0
Revisions in estimated cash flows | 96 | 2
Revisions in discount rates | 16 | (37)
Reversals | 0 | 0
Change in foreign exchange rates | (7) | 7
Liabilities disposed | (23) |
Balance | 501 | 407
Other |  |
Reconciliation of changes in other provisions [abstract] |  |
Balance | 49 | 33
Liabilities incurred | 7 | 17
Liabilities settled | (9) | (10)
Accretion | 0 | 0
Acquisition of liabilities | 3 | 8
Revisions in estimated cash flows | 7 | 3
Revisions in discount rates | 0 | 0
Reversals | (1) | (5)
Change in foreign exchange rates | 0 | 3
Liabilities disposed | (9) |
Balance | $ 45 | $ 49

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- Definition The increase (decrease) in other provisions resulting from a change in discount rate. [Refer: Other provisions] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 37 -IssueDate 2018-01-01 -Paragraph 84 -Subparagraph e -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2018-03-01&anchor=para_84_e&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The increase (decrease) in other provisions resulting from foreign currency exchange rate changes on provisions measured in a currency different from the entity's presentation currency. [Refer: Other provisions] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 37 -IssueDate 2018-01-01 -Paragraph 84 -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2018-03-01&anchor=para_84&doctype=Standard -URIDate 2018-03-16 + Details
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- Definition The amount reversed for unused other provisions. [Refer: Other provisions] + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name IAS -Number 37 -IssueDate 2018-01-01 -Paragraph 84 -Subparagraph d -URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=37&date=2018-03-01&anchor=para_84_d&doctype=Standard -URIDate 2018-03-16 + Details
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