STOCK OPTION AND STOCK UNIT PLANS - Schedule of Outstanding Stock Options (Details) - Incentive Stock Options - CAD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Number
Options outstanding at beginning of year (in shares)	28,729
Options granted (in shares)	5,036
Options exercised (in shares)	(7,328)
Options cancelled or expired (in shares)	(1,113)
Options outstanding at end of year (in shares)	25,324	28,729
Options vested at end of year (in shares)	15,602
Weighted Average Exercise Price
Options outstanding at beginning of year (in Canadian dollars per share)	$ 50.79
Options granted (in Canadian dollars per share)	46.36
Options exercised (in Canadian dollars per share)	49.27
Options cancelled or expired (in Canadian dollars per share)	51.78
Options outstanding at end of year (in Canadian dollars per share)	50.31	$ 50.79
Options vested at end of year (in Canadian dollars per share)	$ 51.33
Weighted Average Remaining Contractual Life (years)
Options outstanding at end of year	5 years 8 months 12 days
Options vested at end of year	4 years 2 months 12 days
Aggregate Intrinsic Value
Options outstanding at end of year	$ 70
Options vested at end of year	37
Stock options, additional disclosures
Total intrinsic value of awards exercised	18	$ 2	$ 66
Cash received on exercise of awards	1	0	3
Total fair value of options vested	$ 17	$ 20	$ 21