ACQUISITIONS - Schedule of Estimated Preliminary Fair Values Assigned to Net Assets (Details) $ in Millions	Mar. 06, 2024 CAD ($)	Mar. 06, 2024 USD ($)	Jan. 02, 2024 CAD ($) promissoryNote	Jan. 02, 2024 USD ($)	Mar. 31, 2025 CAD ($)	Dec. 31, 2024 CAD ($)	Jan. 02, 2024 USD ($) promissoryNote
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Goodwill					$ 36,599,000,000	$ 36,600,000,000
EOG Acquisition
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Current assets	$ 493,000,000
Property, plant and equipment	7,276,000,000
Long-term assets	1,689,000,000
Current liabilities	551,000,000
Long-term debt	2,612,000,000
Other long-term liabilities	1,001,000,000
Deferred income tax liabilities	1,045,000,000
Goodwill	1,603,000,000
Purchase price:
Cash	5,852,000,000
Deferred consideration
Purchase price	5,800,000,000	$ 4,300
Expected credit loss	3,000,000
Overfunded pension plan assets	367,000,000
Regulatory assets	1,200,000,000
Fair value adjustment of long-term debt	478,000,000
Fair value adjustment of regulatory offset	0
EOG Acquisition | Carrying Value
Deferred consideration
Trade receivables	$ 379,000,000
RNG Facilities
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Less Noncontrolling Interest [Abstract]
Current assets			$ 31,000,000
Intangible assets			925,000,000
Property, plant and equipment			174,000,000
Current liabilities			5,000,000
Goodwill			223,000,000
Purchase price:
Cash			584,000,000	$ 439
Deferred consideration
Current portion of long-term debt			550,000,000
Long-term debt			207,000,000
Other adjustments			7,000,000
Purchase price			$ 1,348,000,000	$ 1,000
Amortized on a straight-line basis over an weighted-average useful life (in years)			9 years	9 years
Goodwill expected tax deductible period (in years)			15 years	15 years
Number of non-interest promissory notes | promissoryNote			6				6
Remaining consideration payable, payment period (in years)			2 years	2 years
Consideration transferred, liabilities incurred			$ 757,000,000	$ 568
RNG Facilities | Non-Interest Bearing Promissory Notes | Notes Payable, Other Payables
Deferred consideration
Deferred payments			$ 808,000,000				$ 606
RNG Facilities | Minimum
Deferred consideration
Amortized on a straight-line basis over an expected useful life (in years)			13 years	13 years
RNG Facilities | Maximum
Deferred consideration
Amortized on a straight-line basis over an expected useful life (in years)			42 years	42 years