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	6 Months Ended
	Jun. 30, 2025	Jun. 30, 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 earnings1	42	(38)
Included in OCI	(1)	15
Included in regulatory assets/liabilities	(132)	0
Settlements	160	5
Level 3 net derivative asset/(liability) at end of period	$ 17	$ (149)