RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Fair Value of Derivatives (Details) - CAD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Fair Value of Derivatives
Total net financial asset/(liability)	$ (1,161)	$ (404)
Fair Value
Fair Value of Derivatives
Current derivative assets	426	623
Long-term derivative assets	314	463
Current derivative liabilities	(650)	(738)
Long-term derivative liabilities	(1,251)	(752)
Total net financial asset/(liability)	(1,161)	(404)
Foreign exchange contracts
Fair Value of Derivatives
Total net financial asset/(liability)	(901)	(152)
Foreign exchange contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	74	139
Long-term derivative assets	120	335
Current derivative liabilities	(301)	(128)
Long-term derivative liabilities	(794)	(498)
Total net financial asset/(liability)	(901)	(152)
Interest rate contracts
Fair Value of Derivatives
Total net financial asset/(liability)	(163)	(156)
Interest rate contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	21	65
Long-term derivative assets	92	53
Current derivative liabilities	(15)	(186)
Long-term derivative liabilities	(261)	(88)
Total net financial asset/(liability)	(163)	(156)
Commodity contracts
Fair Value of Derivatives
Total net financial asset/(liability)	(98)	(96)
Commodity contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	330	418
Long-term derivative assets	102	75
Current derivative liabilities	(334)	(423)
Long-term derivative liabilities	(196)	(166)
Total net financial asset/(liability)	(98)	(96)
Other contracts
Fair Value of Derivatives
Total net financial asset/(liability)	1	0
Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	1	1
Current derivative liabilities		(1)
Total net financial asset/(liability)	1	0
Level 1 | Fair Value
Fair Value of Derivatives
Current derivative assets	59	142
Long-term derivative assets	1	0
Current derivative liabilities	(42)	(136)
Long-term derivative liabilities	(1)	0
Total net financial asset/(liability)	17	6
Level 1 | Foreign exchange contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	0	0
Long-term derivative assets	0	0
Current derivative liabilities	0	0
Long-term derivative liabilities	0	0
Total net financial asset/(liability)	0	0
Level 1 | Interest rate contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	0	0
Long-term derivative assets	0	0
Current derivative liabilities	0	0
Long-term derivative liabilities	0	0
Total net financial asset/(liability)	0	0
Level 1 | Commodity contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	59	142
Long-term derivative assets	1	0
Current derivative liabilities	(42)	(136)
Long-term derivative liabilities	(1)	0
Total net financial asset/(liability)	17	6
Level 1 | Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	0	0
Current derivative liabilities		0
Total net financial asset/(liability)	0	0
Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets	185	308
Long-term derivative assets	231	412
Current derivative liabilities	(407)	(391)
Long-term derivative liabilities	(1,078)	(608)
Total net financial asset/(liability)	(1,069)	(279)
Level 2 | Foreign exchange contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	74	139
Long-term derivative assets	120	335
Current derivative liabilities	(301)	(128)
Long-term derivative liabilities	(794)	(498)
Total net financial asset/(liability)	(901)	(152)
Level 2 | Interest rate contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	21	65
Long-term derivative assets	92	53
Current derivative liabilities	(15)	(186)
Long-term derivative liabilities	(261)	(88)
Total net financial asset/(liability)	(163)	(156)
Level 2 | Commodity contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	89	103
Long-term derivative assets	19	24
Current derivative liabilities	(91)	(76)
Long-term derivative liabilities	(23)	(22)
Total net financial asset/(liability)	(6)	29
Level 2 | Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	1	1
Current derivative liabilities		(1)
Total net financial asset/(liability)	1	0
Level 3
Fair Value of Derivatives
Total net financial asset/(liability)	(109)
Level 3 | Fair Value
Fair Value of Derivatives
Current derivative assets	182	173
Long-term derivative assets	82	51
Current derivative liabilities	(201)	(211)
Long-term derivative liabilities	(172)	(144)
Total net financial asset/(liability)	(109)	(131)
Level 3 | Foreign exchange contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	0	0
Long-term derivative assets	0	0
Current derivative liabilities	0	0
Long-term derivative liabilities	0	0
Total net financial asset/(liability)	0	0
Level 3 | Interest rate contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	0	0
Long-term derivative assets	0	0
Current derivative liabilities	0	0
Long-term derivative liabilities	0	0
Total net financial asset/(liability)	0	0
Level 3 | Commodity contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	182	173
Long-term derivative assets	82	51
Current derivative liabilities	(201)	(211)
Long-term derivative liabilities	(172)	(144)
Total net financial asset/(liability)	(109)	(131)
Level 3 | Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	0	0
Current derivative liabilities		0
Total net financial asset/(liability)	$ 0	$ 0