RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Fair Value of Derivatives (Details) - CAD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Fair Value of Derivatives
Current derivative assets	$ 557	$ 623
Current derivative liabilities	(1,335)	(738)
Total net derivative asset/(liability)	(2,250)	(404)
Fair Value
Fair Value of Derivatives
Current derivative assets	557	623
Long-term derivative assets	426	463
Current derivative liabilities	(1,335)	(738)
Long-term derivative liabilities	(1,898)	(752)
Total net derivative asset/(liability)	(2,250)	(404)
Level 1 | Fair Value
Fair Value of Derivatives
Current derivative assets	34	142
Long-term derivative assets	1	0
Current derivative liabilities	(52)	(136)
Long-term derivative liabilities	(1)	0
Total net derivative asset/(liability)	(18)	6
Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets	267	308
Long-term derivative assets	243	412
Current derivative liabilities	(1,000)	(391)
Long-term derivative liabilities	(1,690)	(608)
Total net derivative asset/(liability)	(2,180)	(279)
Level 3
Fair Value of Derivatives
Total net derivative asset/(liability)	(52)
Level 3 | Fair Value
Fair Value of Derivatives
Current derivative assets	256	173
Long-term derivative assets	182	51
Current derivative liabilities	(283)	(211)
Long-term derivative liabilities	(207)	(144)
Total net derivative asset/(liability)	(52)	(131)
Foreign exchange contracts
Fair Value of Derivatives
Total net derivative asset/(liability)	(2,175)	(152)
Foreign exchange contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	125	139
Long-term derivative assets	83	335
Current derivative liabilities	(804)	(128)
Long-term derivative liabilities	(1,579)	(498)
Total net derivative asset/(liability)	(2,175)	(152)
Foreign exchange contracts | Level 1 | 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 derivative asset/(liability)	0	0
Foreign exchange contracts | Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets	125	139
Long-term derivative assets	83	335
Current derivative liabilities	(804)	(128)
Long-term derivative liabilities	(1,579)	(498)
Total net derivative asset/(liability)	(2,175)	(152)
Foreign exchange contracts | Level 3 | 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 derivative asset/(liability)	0	0
Interest rate contracts
Fair Value of Derivatives
Total net derivative asset/(liability)	53	(156)
Interest rate contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	67	65
Long-term derivative assets	146	53
Current derivative liabilities	(80)	(186)
Long-term derivative liabilities	(80)	(88)
Total net derivative asset/(liability)	53	(156)
Interest rate contracts | Level 1 | 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 derivative asset/(liability)	0	0
Interest rate contracts | Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets	67	65
Long-term derivative assets	146	53
Current derivative liabilities	(80)	(186)
Long-term derivative liabilities	(80)	(88)
Total net derivative asset/(liability)	53	(156)
Interest rate contracts | Level 3 | 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 derivative asset/(liability)	0	0
Commodity contracts
Fair Value of Derivatives
Total net derivative asset/(liability)	(131)	(96)
Commodity contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	362	418
Long-term derivative assets	197	75
Current derivative liabilities	(451)	(423)
Long-term derivative liabilities	(239)	(166)
Total net derivative asset/(liability)	(131)	(96)
Commodity contracts | Level 1 | Fair Value
Fair Value of Derivatives
Current derivative assets	34	142
Long-term derivative assets	1	0
Current derivative liabilities	(52)	(136)
Long-term derivative liabilities	(1)	0
Total net derivative asset/(liability)	(18)	6
Commodity contracts | Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets	72	103
Long-term derivative assets	14	24
Current derivative liabilities	(116)	(76)
Long-term derivative liabilities	(31)	(22)
Total net derivative asset/(liability)	(61)	29
Commodity contracts | Level 3 | Fair Value
Fair Value of Derivatives
Current derivative assets	256	173
Long-term derivative assets	182	51
Current derivative liabilities	(283)	(211)
Long-term derivative liabilities	(207)	(144)
Total net derivative asset/(liability)	(52)	(131)
Other contracts
Fair Value of Derivatives
Total net derivative asset/(liability)	3	0
Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	3	1
Long-term derivative assets	0
Current derivative liabilities	0	(1)
Long-term derivative liabilities	0
Total net derivative asset/(liability)	3	0
Other contracts | Level 1 | Fair Value
Fair Value of Derivatives
Current derivative assets	0	0
Long-term derivative assets	0
Current derivative liabilities	0	0
Long-term derivative liabilities	0
Total net derivative asset/(liability)	0	0
Other contracts | Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets	3	1
Long-term derivative assets	0
Current derivative liabilities	0	(1)
Long-term derivative liabilities	0
Total net derivative asset/(liability)	3	0
Other contracts | Level 3 | Fair Value
Fair Value of Derivatives
Current derivative assets	0	0
Long-term derivative assets	0
Current derivative liabilities	0	0
Long-term derivative liabilities	0
Total net derivative asset/(liability)	$ 0	$ 0