RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Changes in Level 3 (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Changes in net fair value of derivative assets and liabilities classified as Level 3
Level 3 net derivative liability at beginning of year	$ (131)	$ (136)
Total gain/(loss), unrealized
Included in earnings	(92)	(48)
Included in OCI	19	67
Included in regulatory assets/liabilities	130	0
Settlements	22	(14)
Level 3 net derivative liability at end of year	$ (52)	$ (131)
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Earnings
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Other Comprehensive Income or Comprehensive Income [Extensible Enumeration]	Other Comprehensive Income (Loss), Net of Tax