RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Schedule of Derivative Assets and Liabilities Measured at Fair Value (Details) - CAD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Fair Value of Derivatives
Total net derivative asset/(liability)	$ (2,209)	$ (2,250)
Fair Value
Fair Value of Derivatives
Current derivative assets	481	557
Long-term derivative assets	371	426
Current derivative liabilities	(1,263)	(1,335)
Long-term derivative liabilities	(1,798)	(1,898)
Total net derivative asset/(liability)	(2,209)	(2,250)
Level 1 | Fair Value
Fair Value of Derivatives
Current derivative assets	30	34
Long-term derivative assets	0	1
Current derivative liabilities	(49)	(52)
Long-term derivative liabilities	0	(1)
Total net derivative asset/(liability)	(19)	(18)
Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets	123	267
Long-term derivative assets	192	243
Current derivative liabilities	(893)	(1,000)
Long-term derivative liabilities	(1,669)	(1,690)
Total net derivative asset/(liability)	(2,247)	(2,180)
Level 3
Fair Value of Derivatives
Total net derivative asset/(liability)	57
Level 3 | Fair Value
Fair Value of Derivatives
Current derivative assets	328	256
Long-term derivative assets	179	182
Current derivative liabilities	(321)	(283)
Long-term derivative liabilities	(129)	(207)
Total net derivative asset/(liability)	57	(52)
Foreign exchange contracts
Fair Value of Derivatives
Total net derivative asset/(liability)	(2,173)	(2,175)
Foreign exchange contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	26	125
Long-term derivative assets	68	83
Current derivative liabilities	(744)	(804)
Long-term derivative liabilities	(1,523)	(1,579)
Total net derivative asset/(liability)	(2,173)	(2,175)
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	26	125
Long-term derivative assets	68	83
Current derivative liabilities	(744)	(804)
Long-term derivative liabilities	(1,523)	(1,579)
Total net derivative asset/(liability)	(2,173)	(2,175)
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)	(21)	53
Interest rate contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	21	67
Long-term derivative assets	107	146
Current derivative liabilities	(36)	(80)
Long-term derivative liabilities	(113)	(80)
Total net derivative asset/(liability)	(21)	53
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	21	67
Long-term derivative assets	107	146
Current derivative liabilities	(36)	(80)
Long-term derivative liabilities	(113)	(80)
Total net derivative asset/(liability)	(21)	53
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)	(15)	(131)
Commodity contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	434	362
Long-term derivative assets	196	197
Current derivative liabilities	(483)	(451)
Long-term derivative liabilities	(162)	(239)
Total net derivative asset/(liability)	(15)	(131)
Commodity contracts | Level 1 | Fair Value
Fair Value of Derivatives
Current derivative assets	30	34
Long-term derivative assets	0	1
Current derivative liabilities	(49)	(52)
Long-term derivative liabilities	0	(1)
Total net derivative asset/(liability)	(19)	(18)
Commodity contracts | Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets	76	72
Long-term derivative assets	17	14
Current derivative liabilities	(113)	(116)
Long-term derivative liabilities	(33)	(31)
Total net derivative asset/(liability)	(53)	(61)
Commodity contracts | Level 3 | Fair Value
Fair Value of Derivatives
Current derivative assets	328	256
Long-term derivative assets	179	182
Current derivative liabilities	(321)	(283)
Long-term derivative liabilities	(129)	(207)
Total net derivative asset/(liability)	$ 57	(52)
Other contracts
Fair Value of Derivatives
Total net derivative asset/(liability)		3
Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets		3
Total net derivative asset/(liability)		3
Other contracts | Level 1 | Fair Value
Fair Value of Derivatives
Current derivative assets		0
Total net derivative asset/(liability)		0
Other contracts | Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets		3
Total net derivative asset/(liability)		3
Other contracts | Level 3 | Fair Value
Fair Value of Derivatives
Current derivative assets		0
Total net derivative asset/(liability)		$ 0