STOCK OPTION AND STOCK UNIT PLANS - PSUs and RSUs (Details) - CAD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Number
Dividend reinvestment (in shares)	237
Performance Stock Units (PSUs)
Number
Units outstanding at beginning of year (in shares)	3,180
Units granted (in shares)	1,444
Units cancelled (in shares)	(104)
Units matured (in shares)	(1,355)
Units outstanding at end of year (in shares)	3,402	3,180
Weighted Average Remaining Contractual Life (years)
Units outstanding at end of year	1 year 7 months 6 days
Aggregate Intrinsic Value
Units outstanding at end of year	$ 244
Stock units, additional disclosures
Total amount paid	$ 65	$ 123	$ 90
Restricted Stock Units (RSU)
Number
Units outstanding at beginning of year (in shares)	3,571
Units granted (in shares)	1,758
Units cancelled (in shares)	(112)
Units matured (in shares)	(1,910)
Dividend reinvestment (in shares)	284
Units outstanding at end of year (in shares)	3,591	3,571
Weighted Average Grant Date Fair Value
Units outstanding at beginning of year	$ 50.69
Units granted	48.50
Units cancelled	51.38
Units matured	49.99
Dividend reinvestment	50.94
Units outstanding at end of year	$ 51.10	$ 50.69
Weighted Average Remaining Contractual Life (years)
Units outstanding at end of year	1 year
Aggregate Intrinsic Value
Units outstanding at end of year	$ 187
Stock units, additional disclosures
Total amount paid	$ 40	$ 56	$ 32