Income Taxes (Reconciliation of Income Tax Expense) (Details) - CAD CAD in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income tax expense reconciliation
Canadian statutory federal tax rate	15.00%	15.00%	15.00%
Income tax expense at the Canadian statutory federal tax rate	CAD 763	CAD 739	CAD 731
Income tax expense (recovery) resulting from:
Provincial and foreign taxes	536	532	550
Deferred income tax adjustments due to rate enactments	(1,706)	7	42
Gain on disposals	(3)	(12)	(11)
Other	15	21	24
Income tax expense (recovery)	(395)	1,287	1,336
Cash payments for income taxes	CAD 712	CAD 653	CAD 725

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The portion of the difference, between total income tax expense (benefit) as reported in the Income Statement for the period and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to provincial and foreign federal, state and local income tax expense (benefit).

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations, attributable to increase (decrease) in the income tax rates.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

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