SEGMENTED INFORMATION - Geographic Information and Property, Plant and Equipment (Details) - CAD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Geographic Information
Revenues	$ 16,217	$ 14,882	$ 11,336	$ 11,038	$ 11,298	$ 9,844	$ 10,432	$ 12,075	$ 53,473	$ 43,649	$ 53,309
Property, plant and equipment, net	131,104				104,641				131,104	104,641	104,460
Canada
Geographic Information
Revenues									22,001	23,781	27,498
Property, plant and equipment, net	48,873				48,570				48,873	48,570
US
Geographic Information
Revenues									31,472	19,868	$ 25,811
Property, plant and equipment, net	$ 82,231				$ 56,071				$ 82,231	$ 56,071