PENSION AND OTHER POSTRETIREMENT BENEFITS - Expected Benefit Payments and Employer Contributions (Details) $ in Millions	Dec. 31, 2023 CAD ($)
Canada \| Pension
Benefits Expected to be Paid by the Company
2024	$ 207
2025	213
2026	219
2027	224
2028	230
2029-2033	1,234
Contributions expected to be paid in next fiscal year	18
Canada \| OPEB
Benefits Expected to be Paid by the Company
2024	13
2025	13
2026	13
2027	13
2028	13
2029-2033	70
Contributions expected to be paid in next fiscal year	13
US \| Pension
Benefits Expected to be Paid by the Company
2024	87
2025	87
2026	87
2027	86
2028	81
2029-2033	393
Contributions expected to be paid in next fiscal year	5
US \| OPEB
Benefits Expected to be Paid by the Company
2024	16
2025	15
2026	14
2027	13
2028	12
2029-2033	49
Contributions expected to be paid in next fiscal year	$ 6

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+ References

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-Topic 715
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-Name Accounting Standards Codification
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Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
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