RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Schedule of Unrealized Gains and Losses Associated With Changes in The Fair Value of Non-Qualifying Derivatives (Details) - CAD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
The Effect of Derivative Instruments on the Statements of Earnings and Comprehensive Income
Unrealized gain (loss) on derivatives	$ 92	$ (693)
Non- Qualifying Derivative Instruments
The Effect of Derivative Instruments on the Statements of Earnings and Comprehensive Income
Unrealized gain (loss) on derivatives	92	(693)
Foreign exchange contracts | Non- Qualifying Derivative Instruments
The Effect of Derivative Instruments on the Statements of Earnings and Comprehensive Income
Unrealized gain (loss) on derivatives	38	(730)
Interest rate contracts | Non- Qualifying Derivative Instruments
The Effect of Derivative Instruments on the Statements of Earnings and Comprehensive Income
Unrealized gain (loss) on derivatives	(73)	105
Commodity contracts | Non- Qualifying Derivative Instruments
The Effect of Derivative Instruments on the Statements of Earnings and Comprehensive Income
Unrealized gain (loss) on derivatives	130	(67)
Commodity contracts | Non- Qualifying Derivative Instruments | Transportation and other services
The Effect of Derivative Instruments on the Statements of Earnings and Comprehensive Income
Unrealized gain (loss) on derivatives	86	(35)
Commodity contracts | Non- Qualifying Derivative Instruments | Commodity sales
The Effect of Derivative Instruments on the Statements of Earnings and Comprehensive Income
Unrealized gain (loss) on derivatives	(24)	(37)
Commodity contracts | Non- Qualifying Derivative Instruments | Commodity costs
The Effect of Derivative Instruments on the Statements of Earnings and Comprehensive Income
Unrealized gain (loss) on derivatives	70	23
Commodity contracts | Non- Qualifying Derivative Instruments | Operating and administrative expense
The Effect of Derivative Instruments on the Statements of Earnings and Comprehensive Income
Unrealized gain (loss) on derivatives	(2)	(18)
Other contracts | Non- Qualifying Derivative Instruments
The Effect of Derivative Instruments on the Statements of Earnings and Comprehensive Income
Unrealized gain (loss) on derivatives	$ (3)	$ (1)