Pensions and Other Postretirement Benefits (Defined Contribution and Other Plans) (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Employer's contributions	$ 22	$ 19	$ 18

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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