PENSION AND OTHER POSTRETIREMENT BENEFITS - Expected Benefit Payments and Employer Contributions (Details) $ in Millions	Dec. 31, 2024 CAD ($)
Canada \| Pension
Benefits Expected to be Paid by the Company
2025	$ 214
2026	220
2027	226
2028	232
2029	238
2030-2034	1,285
Contributions expected to be paid in next fiscal year	21
Canada \| OPEB
Benefits Expected to be Paid by the Company
2025	11
2026	12
2027	12
2028	12
2029	12
2030-2034	64
Contributions expected to be paid in next fiscal year	11
US \| Pension
Benefits Expected to be Paid by the Company
2025	117
2026	120
2027	123
2028	123
2029	120
2030-2034	625
Contributions expected to be paid in next fiscal year	6
US \| OPEB
Benefits Expected to be Paid by the Company
2025	16
2026	16
2027	16
2028	16
2029	16
2030-2034	71
Contributions expected to be paid in next fiscal year	$ 6

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Amount of benefit for defined benefit plan expected to be paid in five fiscal years after fifth fiscal year following current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
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-Publisher FASB
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Amount of contribution expected to be received by defined benefit plan from employer in next fiscal year following current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
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-URI https://asc.fasb.org/1943274/2147480482/715-20-55-18

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