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Other Long-Term Obligations (Parenthetical) (Detail) - CAD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Schedule of Other Liabilities [Line Items] |  |
Employee retirement benefit obligations in current liabilities | $ 58 | $ 55
Asset retirement obligations and other environmental liabilities in current liabilities | $ 124 | $ 118
Asset retirement obligations discount rate | 6.00% | 6.00%

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