PENSION AND OTHER POSTRETIREMENT BENEFITS - Retirement Savings Plan (Details) - United States - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension and Other Postretirement Benefit Disclosures
Percent of match (percent)	6.00%
Total contributions by the Company	$ 30	$ 27	$ 27