Income Taxes - Change in Deferred Income Tax Balances (Details) - CAD CAD in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Reconciliation of changes in deferred tax liability (asset) [abstract]
Beginning of year	CAD 11,180.0	CAD 9,919.0
Recognized in deferred income tax expense	249.0	(512.0)
Recognized in other comprehensive income	19.0	(5.0)
Recognized in equity		(26.0)
Acquisition		2,054.0
Foreign exchange, disposition and other	(15.0)	(179.0)
Reclassified to assets held for sale (note 36 and 37)		(71.0)
End of year	CAD 11,433.0	CAD 11,180.0

The amount of tax expense or income relating to changes in deferred tax liabilities and deferred tax assets, recognised in profit or loss. [Refer: Deferred tax assets; Deferred tax expense (income); Deferred tax liabilities]

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The amount of deferred tax liabilities or assets. [Refer: Deferred tax liabilities; Deferred tax assets]

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The amount of deferred tax related to items credited (charged) directly to equity. [Refer: Deferred tax expense (income)]

+ References

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The amount of income tax relating to amounts recognised in other comprehensive income. [Refer: Other comprehensive income]

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The increase (decrease) in deferred tax liability (asset) resulting from business combinations. [Refer: Deferred tax liability (asset)]

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The increase (decrease) in deferred tax liability (asset) resulting from the net exchange differences arising when the financial statements are translated 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: Deferred tax liability (asset)]

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The decrease in deferred tax liability (asset) resulting from the reclassification to assets held for sale.

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