RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Fair Value of Derivatives (Details) - CAD ($) $ in Millions	Jun. 30, 2023	Dec. 31, 2022
Fair Value of Derivatives
Total net financial asset/(liability)	$ 5	$ (546)
Fair Value
Fair Value of Derivatives
Current derivative assets	632	1,015
Long-term derivative assets	459	627
Current derivative liabilities	(348)	(898)
Long-term derivative liabilities	(738)	(1,290)
Total net financial asset/(liability)	5	(546)
Foreign exchange contracts
Fair Value of Derivatives
Total net financial asset/(liability)	(395)	(1,327)
Foreign exchange contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	129	46
Long-term derivative assets	178	309
Current derivative liabilities	(86)	(566)
Long-term derivative liabilities	(616)	(1,116)
Total net financial asset/(liability)	(395)	(1,327)
Interest rate contracts
Fair Value of Derivatives
Total net financial asset/(liability)	465	910
Interest rate contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	263	660
Long-term derivative assets	213	254
Current derivative liabilities	(2)
Long-term derivative liabilities	(9)	(4)
Total net financial asset/(liability)	465	910
Commodity contracts
Fair Value of Derivatives
Total net financial asset/(liability)	(66)	(139)
Commodity contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	239	302
Long-term derivative assets	68	61
Current derivative liabilities	(260)	(332)
Long-term derivative liabilities	(113)	(170)
Total net financial asset/(liability)	(66)	(139)
Other contracts
Fair Value of Derivatives
Total net financial asset/(liability)	1	10
Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	1	7
Long-term derivative assets		3
Total net financial asset/(liability)	1	10
Level 1 | Fair Value
Fair Value of Derivatives
Current derivative assets	43	65
Long-term derivative assets	0	0
Current derivative liabilities	(21)	(60)
Long-term derivative liabilities	0	0
Total net financial asset/(liability)	22	5
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
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	43	65
Long-term derivative assets	0	0
Current derivative liabilities	(21)	(60)
Long-term derivative liabilities	0	0
Total net financial asset/(liability)	22	5
Level 1 | Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	0	0
Long-term derivative assets		0
Total net financial asset/(liability)	0	0
Level 2 | Fair Value
Fair Value of Derivatives
Current derivative assets	440	803
Long-term derivative assets	408	583
Current derivative liabilities	(127)	(643)
Long-term derivative liabilities	(651)	(1,158)
Total net financial asset/(liability)	70	(415)
Level 2 | Foreign exchange contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	129	46
Long-term derivative assets	178	309
Current derivative liabilities	(86)	(566)
Long-term derivative liabilities	(616)	(1,116)
Total net financial asset/(liability)	(395)	(1,327)
Level 2 | Interest rate contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	263	660
Long-term derivative assets	213	254
Current derivative liabilities	(2)
Long-term derivative liabilities	(9)	(4)
Total net financial asset/(liability)	465	910
Level 2 | Commodity contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	47	90
Long-term derivative assets	17	17
Current derivative liabilities	(39)	(77)
Long-term derivative liabilities	(26)	(38)
Total net financial asset/(liability)	(1)	(8)
Level 2 | Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	1	7
Long-term derivative assets		3
Total net financial asset/(liability)	1	10
Level 3
Fair Value of Derivatives
Total net financial asset/(liability)	(87)
Level 3 | Fair Value
Fair Value of Derivatives
Current derivative assets	149	147
Long-term derivative assets	51	44
Current derivative liabilities	(200)	(195)
Long-term derivative liabilities	(87)	(132)
Total net financial asset/(liability)	(87)	(136)
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
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	149	147
Long-term derivative assets	51	44
Current derivative liabilities	(200)	(195)
Long-term derivative liabilities	(87)	(132)
Total net financial asset/(liability)	(87)	(136)
Level 3 | Other contracts | Fair Value
Fair Value of Derivatives
Current derivative assets	0	0
Long-term derivative assets		0
Total net financial asset/(liability)	$ 0	$ 0