PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 46	$ 48	$ 136	$ 144
Interest cost	40	32	122	96
Expected return on plan assets	(98)	(84)	(294)	(252)
Amortization of actuarial (gain)/loss	(1)	14	(3)	42
Net periodic benefit (credit)/cost	$ (13)	$ 10	$ (39)	$ 30