LEASES - Supplemental Statements of Financial Postion (Details) - CAD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Supplemental Statements Of Financial Position
Operating lease right-of-use assets, net	$ 680	$ 645
Operating lease liabilities - current	87	92
Operating lease liabilities - long-term	677	612
Total	764	704
Finance lease right-of-use assets, net	62	49
Finance lease liabilities - current	17	13
Finance lease liabilities - long-term	39	33
Total finance lease liabilities	$ 56	$ 46
Operating leases - Weighted average remaining lease term	12 years	12 years
Finance leases - Weighted average remaining lease term	5 years	7 years
Operating leases - Weighted average discount rate	4.20%	4.10%
Finance leases - Weighted average discount rate	4.40%	3.80%
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Deferred amounts and other assets	Deferred amounts and other assets
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accounts payable and other (Note 17)	Accounts payable and other (Note 17)
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other long-term liabilities	Other long-term liabilities
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property, plant and equipment, net (Note 11)	Property, plant and equipment, net (Note 11)
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Current portion of long-term debt (Note 18)	Current portion of long-term debt (Note 18)
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other long-term liabilities	Other long-term liabilities
Affiliated Entity
Supplemental Statements Of Financial Position
Operating lease right-of-use assets, net	$ 47	$ 51
Operating lease liabilities - current	5	5
Operating lease liabilities - long-term	$ 43	$ 47