REVENUE - Disaggregation of Revenue (Details) - CAD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 5,174	$ 4,294	$ 11,661	$ 9,685
Total revenues	13,215	10,948	28,312	23,085
Mark-to-market (loss) gain from hedging program	(198)	131	(104)	261
Revenues from lease contracts	143	143	307	302
Revenues from products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20	17	36	34
Revenue from products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	5,154	4,277	11,625	9,651
Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	3,922	3,353	8,052	7,019
Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	246	151	428	309
Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	10	21	17
Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	919	725	3,017	2,259
Total revenues	905	737	3,003	2,277
Electricity and transmission revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	81	55	143	81
Commodity sales
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	8,108	6,334	16,433	12,763
Total revenues	8,108	6,334	16,433	12,763
Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	(67)	320	218	637
Liquids Pipelines
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,629	2,194	5,365	4,549
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	2,629	2,194	5,365	4,549
Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,289	1,119	2,582	2,321
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	1,289	1,119	2,582	2,321
Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,175	926	3,571	2,734
Gas Distribution and Storage | Revenues from products transferred at a point in time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	20	17	36	34
Gas Distribution and Storage | Revenue from products and services transferred over time
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,155	909	3,535	2,700
Renewable Power Generation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	81	55	143	81
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	81	55	143	81
Business segments | Liquids Pipelines
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,629	2,194	5,365	4,549
Total revenues	2,638	2,547	5,693	5,246
Business segments | Liquids Pipelines | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,565	2,157	5,250	4,486
Business segments | Liquids Pipelines | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	64	37	115	63
Business segments | Liquids Pipelines | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	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 and transmission 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	(145)	215	33	427
Business segments | Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,289	1,119	2,582	2,321
Total revenues	1,301	1,128	2,601	2,342
Business segments | Gas Transmission and Midstream | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,200	1,046	2,394	2,167
Business segments | Gas Transmission and Midstream | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	83	63	167	137
Business segments | Gas Transmission and Midstream | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	6	10	21	17
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 and transmission 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	11	9	18	21
Business segments | Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,175	926	3,571	2,734
Total revenues	1,138	953	3,549	2,776
Business segments | Gas Distribution and Storage | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	157	150	408	366
Business segments | Gas Distribution and Storage | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	99	51	146	109
Business segments | Gas Distribution and Storage | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Business segments | Gas Distribution and Storage | Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	919	725	3,017	2,259
Business segments | Gas Distribution and Storage | Electricity and transmission 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	(37)	12	(33)	18
Business segments | Renewable Power Generation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	81	55	143	81
Total revenues	155	132	311	249
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	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 and transmission revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	81	55	143	81
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	74	77	168	168
Business segments | Energy Services
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Total revenues	8,138	6,345	16,475	12,778
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	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 and transmission 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	8,108	6,334	16,433	12,763
Business segments | Energy Services | Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	30	1	32	1
Eliminations and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Total revenues	(155)	(157)	(317)	(306)
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	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 and transmission 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	6	0	2
Intersegment revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	(155)	(163)	(317)	(308)
Total revenues	(155)	(157)	(317)	(306)
Intersegment revenue | Liquids Pipelines
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	154	138	295	270
Intersegment revenue | Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	1	0	1	0
Intersegment revenue | Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	15	11	24
Intersegment revenue | Renewable Power Generation
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	0	0	0
Intersegment revenue | Energy Services
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	$ 0	$ 10	$ 10	$ 14