PENSION AND OTHER POSTRETIREMENT BENEFITS (Details) - CAD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 45	$ 48	$ 90	$ 96
Interest cost	41	32	82	64
Expected return on plan assets	(98)	(84)	(196)	(168)
Amortization of actuarial (gain)/loss	(1)	14	(2)	28
Net periodic benefit (credit)/cost	$ (13)	$ 10	$ (26)	$ 20