STOCK OPTION AND STOCK UNIT PLANS - Stock Option Activity (Details) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2022 CAD ($) compensationPlan $ / shares shares	Dec. 31, 2021 CAD ($) $ / shares shares	Dec. 31, 2020 CAD ($)
STOCK OPTION AND STOCK UNIT PLANS
Number of long-term incentive compensation plans | compensationPlan	3
Compensation expense	$ 260	$ 157	$ 145
INCENTIVE STOCK OPTIONS
STOCK OPTION AND STOCK UNIT PLANS
Compensation expense	$ 15	$ 16	24
Vesting period	4 years
Expiration term	10 years
Number
Options outstanding at beginning of year (in shares) | shares	34,017
Options granted (in shares) | shares	3,430
Options exercised (in shares) | shares	(8,684)
Options cancelled or expired (in shares) | shares	(1,139)
Options outstanding at end of year (in shares) | shares	27,624	34,017
Options vested at end of year (in shares) | shares	17,631
Weighted Average Exercise Price
Options outstanding at beginning of year (in dollars per share) | $ / shares	$ 49.28
Options granted (in dollars per share) | $ / shares	49.58
Options exercised (in dollars per share) | $ / shares	44.55
Options cancelled or expired (in dollars per share) | $ / shares	51.32
Options outstanding at end of year (in dollars per share) | $ / shares	48.46	$ 49.28
Options vested at end of year (in dollars per share) | $ / shares	$ 49.20
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 4 months 24 days
Aggregate Intrinsic Value
Options outstanding at end of year	$ 133
Options vested at end of year	84
Stock options, additional disclosures
Total intrinsic value of awards exercised	66	$ 24	13
Cash received on exercise of awards	3	2	4
Total fair value of options vested	$ 21	$ 25	$ 30