REVENUES - Disaggregation of Revenue from Contract with Customers (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	$ 5,171	$ 5,348	$ 17,976	$ 17,009
Total revenues	9,844	11,573	32,351	39,885
Mark-to-market loss from hedging program	97	345	149	483
Revenues from lease contracts	107	128	387	435
Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	4,298	4,369	13,361	12,421
Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	266	212	784	640
Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers				21
Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	528	699	3,611	3,716
Total revenues	516	695	3,587	3,698
Electricity revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	79	68	220	211
Commodity sales
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	4,652	6,415	14,114	22,880
Total revenues	4,652	6,415	14,114	22,880
Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	21	(190)	261	(4)
Liquids Pipelines
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,921	3,020	8,991	8,385
Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,412	1,355	4,294	3,937
Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	759	905	4,471	4,476
Renewable Power Generation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	79	68	220	211
Business segments | Liquids Pipelines
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,921	3,020	8,991	8,385
Total revenues	3,084	2,899	9,519	8,592
Business segments | Liquids Pipelines | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	2,856	2,962	8,800	8,212
Business segments | Liquids Pipelines | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	65	58	191	173
Business segments | Liquids Pipelines | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers				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	61	(258)	170	(225)
Business segments | Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,412	1,355	4,294	3,937
Total revenues	1,423	1,366	4,324	3,967
Business segments | Gas Transmission and Midstream | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	1,294	1,264	3,968	3,658
Business segments | Gas Transmission and Midstream | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	118	91	326	258
Business segments | Gas Transmission and Midstream | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers				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	11	10	29	28
Business segments | Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	759	905	4,471	4,476
Total revenues	751	909	4,426	4,458
Business segments | Gas Distribution and Storage | Transportation revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	148	143	593	551
Business segments | Gas Distribution and Storage | Storage and other revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	83	63	267	209
Business segments | Gas Distribution and Storage | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers				0
Business segments | Gas Distribution and Storage | Gas distribution sales
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	528	699	3,611	3,716
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	(9)	3	(50)	(30)
Business segments | Renewable Power Generation
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	79	68	220	211
Total revenues	40	120	334	431
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
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	79	68	220	211
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	(42)	54	112	222
Business segments | Energy Services
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Total revenues	4,658	6,419	14,138	22,894
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
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	4,652	6,415	14,114	22,880
Business segments | Energy Services | Other revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	0	0	0
Eliminations and Other
Disaggregation of Revenue [Line Items]
Revenue from contracts with customers	0	0	0	0
Total revenues	(112)	(140)	(390)	(457)
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
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	1	0	1
Intersegment revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	(112)	(141)	(390)	(458)
Total revenues	(112)	(140)	(390)	(457)
Intersegment revenue | Liquids Pipelines
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	102	137	358	432
Intersegment revenue | Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	0	1	1	2
Intersegment revenue | Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	1	1	5	12
Intersegment revenue | Renewable Power Generation
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	3	(2)	2	(2)
Intersegment revenue | Energy Services
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers	$ 6	$ 4	$ 24	$ 14