Goodwill - Summary of Carrying Value of Goodwill (Detail) $ in Millions	12 Months Ended
Dec. 31, 2017 CAD ($)
Disclosure Of Reconciliation Of Changes In Goodwill [Abstract]
Carrying Value, Beginning of Year	$ 242
Goodwill Recognized on Acquisition (Note 9)	2,030
Carrying Value, End of Year	$ 2,272

The amount of assets representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognised. [Refer: Business combinations [member]]

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