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Description of Business and Segmented Disclosures - Additional Information (Detail) $ in Millions | 12 Months Ended
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Dec. 31, 2020 CAD ($) Refinery Customer | Dec. 31, 2019 CAD ($) Customer | Dec. 31, 2018 CAD ($) Customer
Disclosure Of Operating Segments [Line Items] |  |  |
Number of major customers | Customer | 3 | 2 | 3
Gross Sales | $ 13,591 | $ 21,353 | $ 21,389
Customer One [Member] |  |  |
Disclosure Of Operating Segments [Line Items] |  |  |
Gross Sales | 4,323 | 6,922 | 7,840
Customer Two [Member] |  |  |
Disclosure Of Operating Segments [Line Items] |  |  |
Gross Sales | 1,834 | $ 2,316 | 2,285
Customer Three [Member] |  |  |
Disclosure Of Operating Segments [Line Items] |  |  |
Gross Sales | $ 1,472 |  | $ 2,263
Bottom of Range [Member] |  |  |
Disclosure Of Operating Segments [Line Items] |  |  |
Percentage of entity's revenue from gross sales | 10.00% | 10.00% | 10.00%
Canada [Member] |  |  |
Disclosure Of Operating Segments [Line Items] |  |  |
Sales of crude oil, natural gas and NGLs | $ 2,639 | $ 4,002 | $ 2,500
Refining and Marketing [Member] |  |  |
Disclosure Of Operating Segments [Line Items] |  |  |
Number of refineries | Refinery | 2 |  |
Gross Sales | $ 6,051 | $ 10,513 | $ 11,183

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- Definition Export sales of oil and gas products to foreign location. + References No definition available. + Details
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Balance Type: | credit
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- Definition Number of major customers. + References No definition available. + Details
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Balance Type: | na
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- Definition Number of refineries. + References No definition available. + Details
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- Definition Percentage of entities revenues from gross sales. + References No definition available. + Details
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- Definition Income before the deduction of royalty expense. + References No definition available. + Details
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Balance Type: | credit
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- Definition Line items represent concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes of the table. + References No definition available. + Details
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- Details
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Namespace Prefix: |
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- Details
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Period Type: |

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- Details
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Namespace Prefix: |
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Period Type: |

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- Details
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Namespace Prefix: |
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- Details
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Namespace Prefix: |
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- Details
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Namespace Prefix: |
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Balance Type: |
Period Type: |