Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

PENSION AND OTHER POSTRETIREMENT BENEFITS - Retirement Savings Plan (Details) - US - CAD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pension and Other Postretirement Benefit Disclosures
Total contributions by the Company	$ 35	$ 33	$ 30
Minimum
Pension and Other Postretirement Benefit Disclosures
Percent of match (percent)	3.00%
Maximum
Pension and Other Postretirement Benefit Disclosures
Percent of match (percent)	7.00%