RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Fair Value Derivatives (Details) - CAD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Foreign Currency Fair Value Hedge Derivative [Line Items]
Realized loss on derivative	$ (97)	$ (345)	$ (149)	$ (483)
Fair value hedges \| Interest rate contracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Unrealized gain/(loss) on derivative	35	122	(107)	221
Unrealized gain/(loss) on hedged item	(35)	(122)	106	(211)
Realized loss on derivative	(11)	(5)	(34)	(101)
Realized gain on hedged item	$ 0	$ 0	$ 0	$ 85

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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-Topic 815
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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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