RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Schedule of Changes in Net Fair Value of Derivative Assets and Liabilities Classified as Level 3 in the Fair Value Hierarchy (Details) - CAD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Changes in net fair value of derivative assets and liabilities classified as Level 3
Level 3 net derivative liability at beginning of period	$ (52)	$ (131)
Total gain/(loss), unrealized
Included in earnings	23	(17)
Included in OCI	2	12
Included in regulatory assets/liabilities	(45)	0
Settlements	129	9
Level 3 net derivative asset/(liability) at end of period	$ 57	$ (127)