RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Fair Value Derivatives (Details) - CAD ($) $ in Millions	3 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Foreign Currency Fair Value Hedge Derivative [Line Items]
Realized loss on derivative	$ 94	$ 130
Fair value hedges \| Interest rate contracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Unrealized gain/(loss) on derivative	76	(3)
Unrealized loss on hedged item	(87)	(4)
Realized loss on derivative	(75)	(39)
Realized gain on hedged item	$ 85	$ 45

Amount of gain (loss) from the increase (decrease) in fair value of derivative and nonderivative instruments designated as fair value hedging instruments recognized in the income statement.

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Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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Gain (loss) incurred in hedging activities.

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