PENSION AND POST-RETIREMENT AND POST-EMPLOYMENT BENEFITS - Summary of Changes in Fair Value of Financial Instruments Classified in Level 3 (Details) - Level 3 - CAD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024
Change in plan assets
Fair value of plan assets, beginning of year	$ 3,142	$ 2,769
Realized and unrealized gains	136	262
Purchases	138	203
Sales and disbursements	(139)	(92)
Fair value of plan assets, end of year	$ 3,277	$ 3,142

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