Exploration And Evaluation Assets (Details) - CAD CAD in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Goodwill and Other Intangible Assets rollforward
Amortization	CAD (3.0)	CAD (4.0)
Exploration and Evaluation Assets.
Goodwill and Other Intangible Assets rollforward
Beginning of year	2,038.0	1,681.0
Acquisitions and additions	53.0	787.0
Transfers to oil and gas assets		(65.0)
Dry Hole Expenses	(41.0)	(204.0)
Impairment		(152.0)
Amortization	(1.0)	(1.0)
Foreign exchange adjustments	3.0	(8.0)
End of year	CAD 2,052.0	CAD 2,038.0

The amount of amortisation of intangible assets other than goodwill. [Refer: Depreciation and amortisation expense; Intangible assets other than goodwill]

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The amount of impairment loss recognised in profit or loss for intangible assets other than goodwill. [Refer: Impairment loss recognised in profit or loss; Intangible assets other than goodwill]

+ References

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The increase (decrease) in intangible assets other than goodwill resulting from net exchange differences arising on the translation of the financial statements from the functional currency into a different presentation currency, including the translation of a foreign operation into the presentation currency of the reporting entity. [Refer: Intangible assets other than goodwill]

+ References

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The increase (decrease) in intangible assets other than goodwill resulting from transfers. [Refer: Intangible assets other than goodwill]

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The amount of identifiable non-monetary assets without physical substance. This amount does not include goodwill. [Refer: Goodwill]

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The increase in intangible assets other than goodwill resulting from acquisitions through business combinations or additions.

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The expenses incurred when an oil well is dug but no oil is found.

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