PENSION AND POST-RETIREMENT AND POST-EMPLOYMENT BENEFITS - Summary of Projected Benefit Obligation (PBO), Accumulated Benefit Obligation (ABO) and Fair Value of Plan Assets (Details) - Pension Benefits - CAD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Pension Plans, Postretirement and Other Employee Benefits [Line Items]
PBO	$ 8,907	$ 8,686	$ 8,665
ABO	8,004	7,848
Fair value of plan assets	$ 9,517	$ 9,333	$ 8,764

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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+ Details