OTHER INCOME/(EXPENSE) (Details) - CAD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Other Income and Expenses [Abstract]
Gain on dispositions	$ 4	$ 1	$ 15	$ 0
Realized foreign currency gain	31	106	177	110
Unrealized foreign currency loss	(652)	(1,129)	(348)	(1,345)
Net defined pension and OPEB credit	34	59	101	176
Other	118	80	267	135
Total	$ (465)	$ (883)	$ 212	$ (924)