RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Fair Value Derivatives (Details) - CAD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Foreign Currency Fair Value Hedge Derivative [Line Items]
Realized loss on derivative	$ (198)	$ 131	$ (104)	$ 261
Fair value hedges \| Interest rate contracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Unrealized gain/(loss) on derivative	23	(32)	99	(35)
Unrealized gain/(loss) on hedged item	(2)	32	(89)	28
Realized loss on derivative	(21)	0	(96)	(39)
Realized gain on hedged item	$ 0	$ 0	$ 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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