RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Fair Value of Derivatives (Details) - CAD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Fair Value of Derivatives
Total net financial asset/(liability)	$ (1,326)	$ (404)
Fair Value
Fair Value of Derivatives
Current derivative assets	469	623
Long-term derivative assets	284	463
Current derivative liabilities	(858)	(738)
Long-term derivative liabilities	(1,221)	(752)
Total net financial asset/(liability)	(1,326)	(404)
Foreign exchange contracts
Fair Value of Derivatives
Total net financial asset/(liability)	(1,177)	(152)
Foreign exchange contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	92	139
Long-term derivative assets	118	335
Current derivative liabilities	(415)	(128)
Long-term derivative liabilities	(972)	(498)
Total net financial asset/(liability)	(1,177)	(152)
Interest rate contracts
Fair Value of Derivatives
Total net financial asset/(liability)	51	(156)
Interest rate contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	107	65
Long-term derivative assets	66	53
Current derivative liabilities	(93)	(186)
Long-term derivative liabilities	(29)	(88)
Total net financial asset/(liability)	51	(156)
Commodity contracts
Fair Value of Derivatives
Total net financial asset/(liability)	(200)	(96)
Commodity contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	270	418
Long-term derivative assets	100	75
Current derivative liabilities	(350)	(423)
Long-term derivative liabilities	(220)	(166)
Total net financial asset/(liability)	(200)	(96)
Other contracts
Fair Value of Derivatives
Total net financial asset/(liability)		0
Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets		1
Current derivative liabilities		(1)
Total net financial asset/(liability)		0
Level 1 | Fair Value
Fair Value of Derivatives
Current derivative assets	23	142
Long-term derivative assets	0	0
Current derivative liabilities	(49)	(136)
Long-term derivative liabilities	0	0
Total net financial asset/(liability)	(26)	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	23	142
Long-term derivative assets	0	0
Current derivative liabilities	(49)	(136)
Long-term derivative liabilities	0	0
Total net financial asset/(liability)	(26)	6
Level 1 | Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets		0
Current derivative liabilities		0
Total net financial asset/(liability)		0
Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets	277	308
Long-term derivative assets	201	412
Current derivative liabilities	(601)	(391)
Long-term derivative liabilities	(1,028)	(608)
Total net financial asset/(liability)	(1,151)	(279)
Level 2 | Foreign exchange contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	92	139
Long-term derivative assets	118	335
Current derivative liabilities	(415)	(128)
Long-term derivative liabilities	(972)	(498)
Total net financial asset/(liability)	(1,177)	(152)
Level 2 | Interest rate contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	107	65
Long-term derivative assets	66	53
Current derivative liabilities	(93)	(186)
Long-term derivative liabilities	(29)	(88)
Total net financial asset/(liability)	51	(156)
Level 2 | Commodity contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	78	103
Long-term derivative assets	17	24
Current derivative liabilities	(93)	(76)
Long-term derivative liabilities	(27)	(22)
Total net financial asset/(liability)	(25)	29
Level 2 | Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets		1
Current derivative liabilities		(1)
Total net financial asset/(liability)		0
Level 3
Fair Value of Derivatives
Total net financial asset/(liability)	(149)
Level 3 | Fair Value
Fair Value of Derivatives
Current derivative assets	169	173
Long-term derivative assets	83	51
Current derivative liabilities	(208)	(211)
Long-term derivative liabilities	(193)	(144)
Total net financial asset/(liability)	(149)	(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	169	173
Long-term derivative assets	83	51
Current derivative liabilities	(208)	(211)
Long-term derivative liabilities	(193)	(144)
Total net financial asset/(liability)	$ (149)	(131)
Level 3 | Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets		0
Current derivative liabilities		0
Total net financial asset/(liability)		$ 0