SEGMENTED INFORMATION - GEOGRAPHIC INFORMATION (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
Geographic Information
Revenues	$ 12,470	$ 11,466	$ 10,948	$ 12,187	$ 10,008	$ 9,110	$ 7,956	$ 12,013	$ 47,071	$ 39,087	$ 50,069
Property, plant and equipment, net	100,067				94,571				100,067	94,571	93,723
Canada
Geographic Information
Revenues									20,474	16,453	19,954
Property, plant and equipment, net	47,102				46,499				47,102	46,499
US
Geographic Information
Revenues									26,597	22,634	$ 30,115
Property, plant and equipment, net	$ 52,965				$ 48,072				$ 52,965	$ 48,072