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ACCOUNTING POLICIES (Details) | 12 Months Ended
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Dec. 31, 2017
Bottom of range | Midstream |
Disclosure of detailed information about property, plant and equipment [line items] |
Estimated useful life | 5 years
Bottom of range | Other equipment | Oil Sands Mining and Upgrading |
Disclosure of detailed information about property, plant and equipment [line items] |
Estimated useful life | 2 years
Top of range | Midstream |
Disclosure of detailed information about property, plant and equipment [line items] |
Estimated useful life | 30 years
Top of range | Other equipment | Oil Sands Mining and Upgrading |
Disclosure of detailed information about property, plant and equipment [line items] |
Estimated useful life | 18 years
Performance Share Units |
Disclosure of detailed information about property, plant and equipment [line items] |
Vesting term | 3 years

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