INCOME TAXES - Narrative (Details) - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Income Taxes
Operating loss carryforwards that do not expire	$ 6,300	$ 7,900
Foreign subsidiaries' undistributed earnings on which deferred income taxes has not been provided	6,600	8,000
Interest and penalties expense (recovery) related to unrecognized tax benefits	1	1
Accrued interest and penalties related to unrecognized tax benefits	14	13
Canada
Income Taxes
Benefit of unused tax loss carryforwards recognized	1,300	2,100
US
Income Taxes
Benefit of unused tax loss carryforwards recognized	6,400	8,100
Operating loss carryforwards that expire	$ 100	$ 200