LONG-TERM INVESTMENTS - Summary of Combined Financial Information (Details) - CAD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income statement information
Operating revenues (Note 4)	$ 11,298	$ 9,844	$ 10,432	$ 12,075	$ 13,424	$ 11,573	$ 13,215	$ 15,097	$ 43,649	$ 53,309	$ 47,071
Earnings	1,568	623	2,001	1,866	(1,109)	1,383	607	2,057	6,058	2,938	6,314
Earnings attributable to controlling interests	1,818	$ 621	$ 1,935	$ 1,817	(983)	$ 1,362	$ 595	$ 2,029	6,191	3,003	6,189
Balance sheet information
Current assets	14,399				12,147				14,399	12,147
Current liabilities	17,435				20,301				17,435	20,301
Noncontrolling interests	3,029				3,511				3,029	3,511
Unconsolidated equity method investments
Income statement information
Operating revenues (Note 4)									22,586	30,026	22,551
Operating expenses									17,111	23,835	17,446
Earnings									4,818	5,123	3,656
Earnings attributable to controlling interests									1,816	2,056	$ 1,600
Balance sheet information
Current assets	5,842				5,328				5,842	5,328
Non-current assets	61,141				61,393				61,141	61,393
Current liabilities	6,194				5,631				6,194	5,631
Non-current liabilities	23,957				23,208				23,957	23,208
Noncontrolling interests	$ 4,124				$ 4,640				$ 4,124	$ 4,640