RISK MANAGEMENT AND FINANCIAL INSTRUMENTS - Restricted Long-Term Investments (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Long-Lived Assets Held-for-sale [Line Items]
Debt securities, available-for-sale, amortized cost	$ 540	$ 486
Unrealized holding gains (losses)	$ 33	$ 51
Fair value recurring basis unobservable input reconciliation asset gain loss statement of other comprehensive income extensible list not disclosed flag	investments	investments
Future abandonment costs	$ 826	$ 745
Total long - term regulatory liabilities	6,112	3,521
Pipeline future abandonment costs
Long-Lived Assets Held-for-sale [Line Items]
Total long - term regulatory liabilities	826	745
Level 1
Long-Lived Assets Held-for-sale [Line Items]
Restricted long-term investments and cash (Note 23)	491	263
Level 2
Long-Lived Assets Held-for-sale [Line Items]
Restricted long-term investments and cash (Note 23)	507	454
Fair Value
Long-Lived Assets Held-for-sale [Line Items]
Restricted long-term investments and cash (Note 23)	$ 998	$ 717