REGULATORY MATTERS - Liquids Pipelines (Narrative) (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Public Utilities, General Disclosures [Line Items]
Regulatory Liabilities	$ 3,828	$ 3,791
Regulatory assets	5,707	6,467
Canadian Mainline
Public Utilities, General Disclosures [Line Items]
Regulatory deferred assets	1,900	$ 2,100
Decrease in regulatory tax asset	160
Deferred tax liabilities, regulatory assets	40
Southern Lights Pipeline
Public Utilities, General Disclosures [Line Items]
Deferred tax liabilities, regulatory assets	$ 23
Pre-determined after-tax rate of return on equity (ROE) (as a percent)	10.00%
Regulatory Liabilities	$ 151
Regulatory assets	$ 92