RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Total Derivative Instruments (Details) - CAD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	$ (1,326)	$ (404)
Derivative liabilities, Total Net Derivative Instruments	$ (1,326)	(404)
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Other current assets
Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	$ (1,215)	(278)
Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	(20)	(122)
Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	(91)	(4)
Other current assets
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	469	623
Derivative assets, Amounts Available for Offset	(239)	(335)
Derivative assets, Total Net Derivative Instruments	230	$ 288
Derivative Asset, Statement of Financial Position [Extensible Enumeration]		Other current assets
Other current assets | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	381	$ 551
Other current assets | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	49	31
Other current assets | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	39	41
Deferred amounts and other assets
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	284	463
Derivative assets, Amounts Available for Offset	(159)	(184)
Derivative assets, Total Net Derivative Instruments	$ 125	$ 279
Derivative Asset, Statement of Financial Position [Extensible Enumeration]	Deferred Costs and Other Assets	Deferred Costs and Other Assets
Deferred amounts and other assets | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	$ 261	$ 396
Deferred amounts and other assets | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	23	51
Deferred amounts and other assets | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	0	16
Other current liabilities
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(858)	(738)
Derivative liabilities, Amounts Available for Offset	239	335
Derivative liabilities, Total Net Derivative Instruments	$ (619)	$ (403)
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Other current liabilities	Other current liabilities
Other current liabilities | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	$ (641)	$ (500)
Other current liabilities | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(87)	(194)
Other current liabilities | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(130)	(44)
Other long-term liabilities
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(1,221)	(752)
Derivative liabilities, Amounts Available for Offset	159	184
Derivative liabilities, Total Net Derivative Instruments	$ (1,062)	$ (568)
Derivative Liability, Statement of Financial Position [Extensible Enumeration]	Other Liabilities, Noncurrent	Other Liabilities, Noncurrent
Other long-term liabilities | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	$ (1,216)	$ (725)
Other long-term liabilities | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(5)	(10)
Other long-term liabilities | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	0	(17)
Foreign exchange contracts
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	(1,177)	(152)
Derivative liabilities, Total Net Derivative Instruments	(1,177)	(152)
Foreign exchange contracts | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	(1,086)	(148)
Foreign exchange contracts | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	0	$ 0
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Other Liabilities, Noncurrent
Foreign exchange contracts | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	(91)	$ (4)
Foreign exchange contracts | Other current assets
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	92	139
Derivative assets, Amounts Available for Offset	(22)	(32)
Derivative assets, Total Net Derivative Instruments	70	107
Foreign exchange contracts | Other current assets | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	53	98
Foreign exchange contracts | Other current assets | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	0	0
Foreign exchange contracts | Other current assets | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	39	41
Foreign exchange contracts | Deferred amounts and other assets
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	118	335
Derivative assets, Amounts Available for Offset	(98)	(122)
Derivative assets, Total Net Derivative Instruments	20	213
Foreign exchange contracts | Deferred amounts and other assets | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	118	319
Foreign exchange contracts | Deferred amounts and other assets | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	0	0
Foreign exchange contracts | Deferred amounts and other assets | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	0	16
Foreign exchange contracts | Other current liabilities
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(415)	(128)
Derivative liabilities, Amounts Available for Offset	22	32
Derivative liabilities, Total Net Derivative Instruments	(393)	(96)
Foreign exchange contracts | Other current liabilities | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(285)	(84)
Foreign exchange contracts | Other current liabilities | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	0	0
Foreign exchange contracts | Other current liabilities | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(130)	(44)
Foreign exchange contracts | Other long-term liabilities
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(972)	(498)
Derivative liabilities, Amounts Available for Offset	98	122
Derivative liabilities, Total Net Derivative Instruments	(874)	(376)
Foreign exchange contracts | Other long-term liabilities | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(972)	(481)
Foreign exchange contracts | Other long-term liabilities | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	0	0
Foreign exchange contracts | Other long-term liabilities | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	0	(17)
Interest rate contracts
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	51	(156)
Derivative assets, Total Net Derivative Instruments	51
Derivative liabilities, Total Net Derivative Instruments		$ (156)
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Other Liabilities, Noncurrent
Interest rate contracts | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	68	$ (52)
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Other Liabilities, Noncurrent
Interest rate contracts | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	(17)	$ (104)
Interest rate contracts | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	0	$ 0
Derivative Liability, Statement of Financial Position [Extensible Enumeration]		Other Liabilities, Noncurrent
Interest rate contracts | Other current assets
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	107	$ 65
Derivative assets, Amounts Available for Offset	(54)	(32)
Derivative assets, Total Net Derivative Instruments	53	33
Interest rate contracts | Other current assets | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	58	34
Interest rate contracts | Other current assets | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	49	31
Interest rate contracts | Other current assets | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	0	0
Interest rate contracts | Deferred amounts and other assets
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	66	53
Derivative assets, Amounts Available for Offset	(10)	(21)
Derivative assets, Total Net Derivative Instruments	56	32
Interest rate contracts | Deferred amounts and other assets | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	43	2
Interest rate contracts | Deferred amounts and other assets | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	23	51
Interest rate contracts | Deferred amounts and other assets | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	0	0
Interest rate contracts | Other current liabilities
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(93)	(186)
Derivative liabilities, Amounts Available for Offset	54	32
Derivative liabilities, Total Net Derivative Instruments	(39)	(154)
Interest rate contracts | Other current liabilities | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(8)	(3)
Interest rate contracts | Other current liabilities | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(85)	(183)
Interest rate contracts | Other current liabilities | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	0	0
Interest rate contracts | Other long-term liabilities
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(29)	(88)
Derivative liabilities, Amounts Available for Offset	10	21
Derivative liabilities, Total Net Derivative Instruments	(19)	(67)
Interest rate contracts | Other long-term liabilities | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(25)	(85)
Interest rate contracts | Other long-term liabilities | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(4)	(3)
Interest rate contracts | Other long-term liabilities | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	0	0
Commodity contracts
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	(200)	(96)
Derivative liabilities, Total Net Derivative Instruments	(200)	(96)
Commodity contracts | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	(197)	(78)
Commodity contracts | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	(3)	(18)
Commodity contracts | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Total net financial asset/(liability)	0	0
Commodity contracts | Other current assets
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	270	418
Derivative assets, Amounts Available for Offset	(163)	(270)
Derivative assets, Total Net Derivative Instruments	107	148
Commodity contracts | Other current assets | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	270	418
Commodity contracts | Other current assets | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	0	0
Commodity contracts | Other current assets | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	0	0
Commodity contracts | Deferred amounts and other assets
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	100	75
Derivative assets, Amounts Available for Offset	(51)	(41)
Derivative assets, Total Net Derivative Instruments	49	34
Commodity contracts | Deferred amounts and other assets | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	100	75
Commodity contracts | Deferred amounts and other assets | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	0	0
Commodity contracts | Deferred amounts and other assets | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets	0	0
Commodity contracts | Other current liabilities
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(350)	(423)
Derivative liabilities, Amounts Available for Offset	163	270
Derivative liabilities, Total Net Derivative Instruments	(187)	(153)
Commodity contracts | Other current liabilities | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(348)	(412)
Commodity contracts | Other current liabilities | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(2)	(11)
Commodity contracts | Other current liabilities | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	0	0
Commodity contracts | Other long-term liabilities
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(220)	(166)
Derivative liabilities, Amounts Available for Offset	51	41
Derivative liabilities, Total Net Derivative Instruments	(169)	(125)
Commodity contracts | Other long-term liabilities | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(219)	(159)
Commodity contracts | Other long-term liabilities | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	(1)	(7)
Commodity contracts | Other long-term liabilities | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative liabilities	$ 0	0
Other contracts
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets		1
Derivative liabilities		(1)
Total net financial asset/(liability)		0
Derivative assets, Amounts Available for Offset		(1)
Derivative liabilities, Amounts Available for Offset		1
Derivative assets, Total Net Derivative Instruments		0
Derivative liabilities, Total Net Derivative Instruments		0
Other contracts | Non- Qualifying Derivative Instruments
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets		1
Derivative liabilities		(1)
Total net financial asset/(liability)		0
Other contracts | Derivative Instruments Used as Cash Flow Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets		0
Derivative liabilities		0
Total net financial asset/(liability)		0
Other contracts | Derivative Instruments Used as Fair Value Hedges | Designated as hedging instrument
TOTAL DERIVATIVE INSTRUMENTS
Derivative assets		0
Derivative liabilities		0
Total net financial asset/(liability)		$ 0