REVENUE (Details) - CAD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									$ 19,432	$ 18,817	$ 19,697
Total operating revenues	$ 12,470	$ 11,466	$ 10,948	$ 12,187	$ 10,008	$ 9,110	$ 7,956	$ 12,013	47,071	39,087	50,069
Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									70	60	69
Transferred over Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									19,362	18,757	19,628
Transportation revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									14,532	14,358	14,302
Storage and other revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									648	571	578
Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									49	27	423
Gas distribution revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									4,026	3,663	4,210
Total operating revenues									4,026	3,663	4,205
Electricity and transmission revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									177	198	180
Commodity sales
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers											4
Revenue not from contract with customers									26,873	19,259	29,305
Total operating revenues									26,873	19,259	29,309
Other Revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									766	1,011	1,067
Liquids Pipelines
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									9,639	9,255	9,191
Liquids Pipelines | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Liquids Pipelines | Transferred over Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									9,639	9,255	9,191
Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									4,668	4,824	5,172
Gas Transmission and Midstream | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	4
Gas Transmission and Midstream | Transferred over Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									4,668	4,824	5,168
Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									4,948	4,540	5,154
Gas Distribution and Storage | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									70	60	65
Gas Distribution and Storage | Transferred over Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									4,878	4,480	5,089
Renewable Power Generation
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									177	198	180
Renewable Power Generation | Transferred at Point in Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Renewable Power Generation | Transferred over Time
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									177	198	180
Business segments | Liquids Pipelines
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									9,639	9,255	9,191
Total operating revenues									10,581	10,423	10,219
Business segments | Liquids Pipelines | Transportation revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									9,492	9,161	9,082
Business segments | Liquids Pipelines | Storage and other revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									147	94	109
Business segments | Liquids Pipelines | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Liquids Pipelines | Gas distribution revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Liquids Pipelines | Electricity and transmission revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Liquids Pipelines | Commodity sales
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers											0
Revenue not from contract with customers									0	0	0
Business segments | Liquids Pipelines | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									375	584	659
Business segments | Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									4,668	4,824	5,172
Total operating revenues									4,711	4,870	5,207
Business segments | Gas Transmission and Midstream | Transportation revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									4,364	4,523	4,477
Business segments | Gas Transmission and Midstream | Storage and other revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									255	274	268
Business segments | Gas Transmission and Midstream | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									49	27	423
Business segments | Gas Transmission and Midstream | Gas distribution revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Gas Transmission and Midstream | Electricity and transmission revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Gas Transmission and Midstream | Commodity sales
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers											4
Revenue not from contract with customers									0	0	0
Business segments | Gas Transmission and Midstream | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									42	44	30
Business segments | Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									4,948	4,540	5,154
Total operating revenues									4,980	4,569	5,179
Business segments | Gas Distribution and Storage | Transportation revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									676	674	743
Business segments | Gas Distribution and Storage | Storage and other revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									246	203	201
Business segments | Gas Distribution and Storage | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Gas Distribution and Storage | Gas distribution revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									4,026	3,663	4,210
Business segments | Gas Distribution and Storage | Electricity and transmission revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Gas Distribution and Storage | Commodity sales
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers											0
Revenue not from contract with customers									0	0	0
Business segments | Gas Distribution and Storage | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									13	17	9
Business segments | Renewable Power Generation
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									177	198	180
Total operating revenues									512	587	567
Business segments | Renewable Power Generation | Transportation revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Renewable Power Generation | Storage and other revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Renewable Power Generation | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Renewable Power Generation | Gas distribution revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Renewable Power Generation | Electricity and transmission revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									177	198	180
Business segments | Renewable Power Generation | Commodity sales
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers											0
Revenue not from contract with customers									0	0	0
Business segments | Renewable Power Generation | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									336	389	387
Business segments | Energy Services
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Total operating revenues									26,917	19,283	29,374
Business segments | Energy Services | Transportation revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Energy Services | Storage and other revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Energy Services | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Energy Services | Gas distribution revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Energy Services | Electricity and transmission revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Business segments | Energy Services | Commodity sales
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers											0
Revenue not from contract with customers									26,873	19,259	29,305
Business segments | Energy Services | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									0	0	(2)
Eliminations and Other
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Total operating revenues									(630)	(645)	(477)
Eliminations and Other | Transportation revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Eliminations and Other | Storage and other revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Eliminations and Other | Gas gathering and processing revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Eliminations and Other | Gas distribution revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Eliminations and Other | Electricity and transmission revenue
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									0	0	0
Eliminations and Other | Commodity sales
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers											0
Revenue not from contract with customers									0	0	0
Eliminations and Other | Other Revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									0	(23)	(16)
Intersegment revenue
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									(630)	(622)	(461)
Intersegment revenue | Liquids Pipelines
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									567	584	369
Intersegment revenue | Gas Transmission and Midstream
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									1	2	5
Intersegment revenue | Gas Distribution and Storage
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									19	12	16
Intersegment revenue | Renewable Power Generation
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									(1)	0	0
Intersegment revenue | Energy Services
Disaggregation of Revenue [Line Items]
Revenue not from contract with customers									$ 44	$ 24	$ 71