LONG-TERM INVESTMENTS - Schedule of Long-Term Investments (Details) - CAD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
LONG-TERM INVESTMENTS
Total long-term investments	$ 13,818	$ 16,528
Noverco Common Shares | Gas Distribution and Storage | Preference shares (Note 21)
LONG-TERM INVESTMENTS
OTHER LONG-TERM INVESTMENTS	567	580
DCP Midstream, LP
LONG-TERM INVESTMENTS
EQUITY INVESTMENTS	$ 331
MarEn Bakken Company LLC1 | Liquids Pipelines
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	75.00%
EQUITY INVESTMENTS	$ 1,795	1,892
MarEn Bakken Company LLC1 | Bakken Pipeline Investments, LLC
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	49.00%
MarEn Bakken Company LLC1 | Bakken Pipeline System
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	27.60%
Gray Oak Holdings LLC | Liquids Pipelines
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	35.00%
EQUITY INVESTMENTS	$ 502	463
Seaway Crude Holdings LLC | Liquids Pipelines
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
EQUITY INVESTMENTS	$ 2,668	2,907
Illinois Extension Pipeline Company, LLC | Liquids Pipelines
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	65.00%
EQUITY INVESTMENTS	$ 623	662
Other | Liquids Pipelines
LONG-TERM INVESTMENTS
EQUITY INVESTMENTS	$ 73	73
Other | Liquids Pipelines | Minimum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	30.00%
Other | Liquids Pipelines | Maximum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	43.80%
Other | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
EQUITY INVESTMENTS	$ 4	5
Other | Gas Transmission and Midstream | Minimum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	33.30%
Other | Gas Transmission and Midstream | Maximum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
Other | Gas Distribution and Storage | Common Shares
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
EQUITY INVESTMENTS	$ 13	14
Other | Renewable Power Generation
LONG-TERM INVESTMENTS
EQUITY INVESTMENTS	$ 196	127
Other | Renewable Power Generation | Minimum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	21.00%
Other | Renewable Power Generation | Maximum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
Other | Eliminations and Other
LONG-TERM INVESTMENTS
EQUITY INVESTMENTS	$ 32	16
Other | Eliminations and Other | Minimum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	30.00%
Other | Eliminations and Other | Maximum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
Alliance Pipeline | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
EQUITY INVESTMENTS	$ 269	310
Aux Sable4 | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
EQUITY INVESTMENTS	$ 251	267
Aux Sable4 | Gas Transmission and Midstream | Minimum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	42.70%
Aux Sable4 | Gas Transmission and Midstream | Maximum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
DCP Midstream, LLC | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
EQUITY INVESTMENTS	$ 331	2,193
DCP Midstream, LLC | DCP Midstream, LP
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	56.50%
Gulfstream Natural Gas System, L.L.C. | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
EQUITY INVESTMENTS	$ 1,175	1,213
Nexus Gas Transmission, LLC | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
EQUITY INVESTMENTS	$ 1,745	1,778
PennEast Pipeline Company, LLC | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	20.00%
EQUITY INVESTMENTS	$ 116	106
Sabal Trail Transmission, LLC | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
EQUITY INVESTMENTS	$ 1,510	1,533
Southeast Supply Header, LLC | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
EQUITY INVESTMENTS	$ 84	484
Steckman Ridge, LP | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
EQUITY INVESTMENTS	$ 90	222
Vector Pipeline L.P. | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	60.00%
EQUITY INVESTMENTS	$ 201	195
Offshore - various joint ventures | Gas Transmission and Midstream
LONG-TERM INVESTMENTS
EQUITY INVESTMENTS	$ 338	$ 362
Offshore - various joint ventures | Gas Transmission and Midstream | Minimum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	22.00%
Offshore - various joint ventures | Gas Transmission and Midstream | Maximum
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	74.30%
Noverco Common Shares | Gas Distribution and Storage | Common Shares
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	38.90%	38.90%
EQUITY INVESTMENTS	$ 156	$ 95
Éolien Maritime France SAS | Renewable Power Generation
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	50.00%
EQUITY INVESTMENTS	$ 96	67
Enbridge Renewable Infrastructure Investments S.a.r.l. (ERII) | Renewable Power Generation
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	51.00%
EQUITY INVESTMENTS	$ 100	141
Rampion Offshore Wind Limited | Renewable Power Generation
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	24.90%
EQUITY INVESTMENTS	$ 599	600
Emerging Technologies and Other | Renewable Power Generation
LONG-TERM INVESTMENTS
OTHER LONG-TERM INVESTMENTS	32	78
Other long-term investments | Eliminations and Other
LONG-TERM INVESTMENTS
OTHER LONG-TERM INVESTMENTS	$ 252	$ 145
Bakken Pipeline Investments, LLC | Bakken Pipeline System
LONG-TERM INVESTMENTS
Ownership Interest (as a percent)	75.00%