RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Schedule of Derivative Assets and Liabilities Measured at Fair Value (Details) - CAD ($) $ in Millions	Jun. 30, 2026	Dec. 31, 2025
Fair Value of Derivatives
Total net derivative asset/(liability)	$ (1,318)	$ (823)
Fair Value
Fair Value of Derivatives
Current derivative assets	1,090	591
Long-term derivative assets	320	293
Current derivative liabilities	(1,306)	(712)
Long-term derivative liabilities	(1,422)	(995)
Total net derivative asset/(liability)	(1,318)	(823)
Level 1 \| Fair Value
Fair Value of Derivatives
Current derivative assets	401	70
Long-term derivative assets	16	0
Current derivative liabilities	(276)	(55)
Long-term derivative liabilities	(18)	0
Total net derivative asset/(liability)	123	15
Level 2 \| Fair Value
Fair Value of Derivatives
Current derivative assets	226	192
Long-term derivative assets	226	176
Current derivative liabilities	(745)	(480)
Long-term derivative liabilities	(1,327)	(914)
Total net derivative asset/(liability)	(1,620)	(1,026)
Level 3
Fair Value of Derivatives
Total net derivative asset/(liability)	179
Level 3 \| Fair Value
Fair Value of Derivatives
Current derivative assets	463	329
Long-term derivative assets	78	117
Current derivative liabilities	(285)	(177)
Long-term derivative liabilities	(77)	(81)
Total net derivative asset/(liability)	179	188
Foreign exchange contracts
Fair Value of Derivatives
Total net derivative asset/(liability)	(1,737)	(1,104)
Foreign exchange contracts \| Fair Value
Fair Value of Derivatives
Current derivative assets	26	27
Long-term derivative assets	28	52
Current derivative liabilities	(645)	(364)
Long-term derivative liabilities	(1,146)	(819)
Total net derivative asset/(liability)	(1,737)	(1,104)
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	27
Long-term derivative assets	28	52
Current derivative liabilities	(645)	(364)
Long-term derivative liabilities	(1,146)	(819)
Total net derivative asset/(liability)	(1,737)	(1,104)
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)	106	91
Interest rate contracts \| Fair Value
Fair Value of Derivatives
Current derivative assets	125	106
Long-term derivative assets	189	117
Current derivative liabilities	(40)	(48)
Long-term derivative liabilities	(168)	(84)
Total net derivative asset/(liability)	106	91
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	125	106
Long-term derivative assets	189	117
Current derivative liabilities	(40)	(48)
Long-term derivative liabilities	(168)	(84)
Total net derivative asset/(liability)	106	91
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)	313	190
Commodity contracts \| Fair Value
Fair Value of Derivatives
Current derivative assets	939	458
Long-term derivative assets	103	124
Current derivative liabilities	(621)	(300)
Long-term derivative liabilities	(108)	(92)
Total net derivative asset/(liability)	313	190
Commodity contracts \| Level 1 \| Fair Value
Fair Value of Derivatives
Current derivative assets	401	70
Long-term derivative assets	16	0
Current derivative liabilities	(276)	(55)
Long-term derivative liabilities	(18)	0
Total net derivative asset/(liability)	123	15
Commodity contracts \| Level 2 \| Fair Value
Fair Value of Derivatives
Current derivative assets	75	59
Long-term derivative assets	9	7
Current derivative liabilities	(60)	(68)
Long-term derivative liabilities	(13)	(11)
Total net derivative asset/(liability)	11	(13)
Commodity contracts \| Level 3 \| Fair Value
Fair Value of Derivatives
Current derivative assets	463	329
Long-term derivative assets	78	117
Current derivative liabilities	(285)	(177)
Long-term derivative liabilities	(77)	(81)
Total net derivative asset/(liability)	$ 179	$ 188

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