PENSION AND POST-RETIREMENT AND POST-EMPLOYMENT BENEFITS - Summary of Estimated Future Benefit Payments (Details) $ in Millions	Dec. 31, 2025 CAD ($)
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2027	$ 73
2028	77
2029	81
2030	85
Pension Benefits
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2026	427
2027	433
2028	439
2029	445
2030	452
2031 through to 2035	2,397
Total estimated future benefit payments through to 2035	4,593
Post-Retirement and Post-Employment Benefits
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
2026	78
2027	78
2028	78
2029	79
2030	80
2031 through to 2035	423
Total estimated future benefit payments through to 2035	$ 816

Defined benefit plan expected future benefit payments.

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- Definition

Pension Plans, Postretirement and Other Employee Benefits [Line Items]

+ References

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- Definition

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 5
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

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- Definition

Amount of benefit for defined benefit plan expected to be paid in next fiscal year following current fiscal year.

+ References

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- Definition

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

+ References

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- Definition

Amount of benefit for defined benefit plan expected to be paid in fourth fiscal year following current fiscal year.

+ References

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- Definition

Amount of benefit for defined benefit plan expected to be paid in third fiscal year following current fiscal year.

+ References

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- Definition

Amount of benefit for defined benefit plan expected to be paid in second fiscal year following current fiscal year.

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