REVENUES - Disaggregation of Revenue (Details) - CAD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 5,592	$ 5,174	$ 12,805	$ 11,661
Total revenues	10,432	13,215	22,507	28,312
Mark-to-market (loss) gain from hedging program	(3)	198	(52)	104
Revenues from lease contracts	136	143	280	307
Revenues from products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	37	20	67	36
Revenue from products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5,555	5,154	12,738	11,625
Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4,461	3,922	9,063	8,052
Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	260	246	518	428
Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		6		21
Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	796	919	3,083	3,017
Total revenues	792	905	3,071	3,003
Electricity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	75	81	141	143
Commodity sales
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	4,679	8,108	9,462	16,433
Total revenues	4,679	8,108	9,462	16,433
Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	161	(67)	240	218
Liquids Pipelines
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,064	2,629	6,070	5,365
Liquids Pipelines | Revenues from products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Liquids Pipelines | Revenue from products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,064	2,629	6,070	5,365
Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,403	1,289	2,882	2,582
Gas Transmission and Midstream | Revenues from products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Gas Transmission and Midstream | Revenue from products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,403	1,289	2,882	2,582
Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,050	1,175	3,712	3,571
Gas Distribution and Storage | Revenues from products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	37	20	67	36
Gas Distribution and Storage | Revenue from products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,013	1,155	3,645	3,535
Renewable Power Generation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	75	81	141	143
Renewable Power Generation | Revenues from products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Renewable Power Generation | Revenue from products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	75	81	141	143
Business segments | Liquids Pipelines
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,064	2,629	6,070	5,365
Total revenues	3,270	2,638	6,435	5,693
Business segments | Liquids Pipelines | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,002	2,565	5,944	5,250
Business segments | Liquids Pipelines | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	62	64	126	115
Business segments | Liquids Pipelines | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		0		0
Business segments | Liquids Pipelines | Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Liquids Pipelines | Electricity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Liquids Pipelines | Commodity sales
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	0	0	0
Business segments | Liquids Pipelines | Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	79	(145)	109	33
Business segments | Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,403	1,289	2,882	2,582
Total revenues	1,410	1,301	2,901	2,601
Business segments | Gas Transmission and Midstream | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,290	1,200	2,674	2,394
Business segments | Gas Transmission and Midstream | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	113	83	208	167
Business segments | Gas Transmission and Midstream | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		6		21
Business segments | Gas Transmission and Midstream | Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Gas Transmission and Midstream | Electricity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Gas Transmission and Midstream | Commodity sales
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	0	0	0
Business segments | Gas Transmission and Midstream | Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	7	11	18	18
Business segments | Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,050	1,175	3,712	3,571
Total revenues	1,050	1,138	3,675	3,549
Business segments | Gas Distribution and Storage | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	169	157	445	408
Business segments | Gas Distribution and Storage | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	85	99	184	146
Business segments | Gas Distribution and Storage | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		0		0
Business segments | Gas Distribution and Storage | Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	796	919	3,083	3,017
Business segments | Gas Distribution and Storage | Electricity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Gas Distribution and Storage | Commodity sales
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	0	0	0
Business segments | Gas Distribution and Storage | Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	(1)	(37)	(41)	(33)
Business segments | Renewable Power Generation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	75	81	141	143
Total revenues	150	155	294	311
Business segments | Renewable Power Generation | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Renewable Power Generation | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Renewable Power Generation | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		0		0
Business segments | Renewable Power Generation | Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Renewable Power Generation | Electricity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	75	81	141	143
Business segments | Renewable Power Generation | Commodity sales
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	0	0	0
Business segments | Renewable Power Generation | Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	76	74	154	168
Business segments | Energy Services
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Total revenues	4,679	8,138	9,480	16,475
Business segments | Energy Services | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Energy Services | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Energy Services | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		0		0
Business segments | Energy Services | Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Energy Services | Electricity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Energy Services | Commodity sales
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	4,679	8,108	9,462	16,433
Business segments | Energy Services | Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	30	0	32
Eliminations and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Total revenues	(127)	(155)	(278)	(317)
Eliminations and Other | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Eliminations and Other | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Eliminations and Other | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers		0		0
Eliminations and Other | Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Eliminations and Other | Electricity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Eliminations and Other | Commodity sales
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	0	0	0
Eliminations and Other | Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	0	0	0
Intersegment revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	(127)	(155)	(278)	(317)
Total revenues	(127)	(155)	(278)	(317)
Intersegment revenue | Liquids Pipelines
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	127	154	256	295
Intersegment revenue | Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	1	1	1
Intersegment revenue | Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	1	0	4	11
Intersegment revenue | Renewable Power Generation
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	(1)	0	(1)	0
Intersegment revenue | Energy Services
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	$ 0	$ 0	$ 18	$ 10