RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Fair Value Derivatives (Details) - CAD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Foreign Currency Fair Value Hedge Derivative [Line Items]
Realized gain/(loss) on derivative	$ 54	$ (97)	$ 15	$ (149)
Fair value hedges \| Interest rate contracts
Foreign Currency Fair Value Hedge Derivative [Line Items]
Unrealized gain/(loss) on derivative	71	35	(21)	(107)
Unrealized gain/(loss) on hedged item	(67)	(35)	33	106
Realized gain/(loss) on derivative	(11)	(11)	36	(34)
Realized loss on hedged item	$ 0	$ 0	$ (79)	$ 0

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
-SubTopic 25
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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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-Topic 815
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Gain (loss) incurred in hedging activities.

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