FINANCIAL INSTRUMENTS AND RISK MANAGEMENT - Non Designated Derivative Financial Instruments (Details) - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Derivative financial instrument assets and liabilities and assets available for sale measured at fair value
Fair value outstanding, beginning of year	$ 89,579
Fair value outstanding, end of year	89,435	$ 89,579
At fair value
Derivative financial instrument assets and liabilities and assets available for sale measured at fair value
Fair value outstanding, beginning of year		(105)
Cash Settlements - received during the year	(254)	(90)
Fair value outstanding, end of year	(39)
Fair value outstanding, beginning of year	60
Changes in fair value recognized in earnings during the year (note 7)	$ 155	255
Fair value outstanding, end of year		$ 60

Expiry date 2020-01-01: The amount of resources: (a) controlled by the entity as a result of past events; and (b) from which future economic benefits are expected to flow to the entity. Effective 2020-01-01: The amount of a present economic resource controlled by the entity as a result of past events. Economic resource is a right that has the potential to produce economic benefits.

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