LEASES - NARRATIVE (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Operating lease, expense	$ 95	$ 107
Operating lease, payments	$ 118	$ 133
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term	5 months
Lessor, operating lease, remaining lease term	1 month
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term	25 years
Lessor, operating lease, remaining lease term	30 years