QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - CAD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Operating revenues	$ 11,298	$ 9,844	$ 10,432	$ 12,075	$ 13,424	$ 11,573	$ 13,215	$ 15,097	$ 43,649	$ 53,309	$ 47,071
Operating income	1,845	1,794	2,350	2,662	(540)	1,778	1,520	2,420	8,651	5,178	7,805
Earnings/(loss)	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
Earnings/(loss) attributable to common shareholders	$ 1,726	$ 532	$ 1,848	$ 1,733	$ (1,067)	$ 1,279	$ 450	$ 1,927	$ 5,839	$ 2,589	$ 5,816
Earnings per common share
Basic (in CAD per share)	$ 0.81	$ 0.26	$ 0.91	$ 0.86	$ (0.53)	$ 0.63	$ 0.22	$ 0.95	$ 2.84	$ 1.28	$ 2.87
Diluted (in CAD per share)	$ 0.81	$ 0.26	$ 0.91	$ 0.85	$ (0.53)	$ 0.63	$ 0.22	$ 0.95	$ 2.84	$ 1.28	$ 2.87