v3.26.1
EMPLOYEE BENEFITS OBLIGATIONS - Significant Assumptions (Details)
$ in Millions
Mar. 31, 2026
CAD ($)
Disclosure of defined benefit plans [line items]  
Change in significant assumptions (in percent) 0.25%
Discount rate:  
Disclosure of defined benefit plans [line items]  
Increase (decrease) in discount rate $ (28.6)
Increase (decrease) in compensation rate 30.8
Compensation rate:  
Disclosure of defined benefit plans [line items]  
Increase (decrease) in discount rate 11.3
Increase (decrease) in compensation rate (10.8)
Canadian | Discount rate: | Funded plans  
Disclosure of defined benefit plans [line items]  
Increase (decrease) in discount rate (25.6)
Increase (decrease) in compensation rate 27.6
Canadian | Discount rate: | Unfunded plans  
Disclosure of defined benefit plans [line items]  
Increase (decrease) in discount rate (2.6)
Increase (decrease) in compensation rate 2.7
Canadian | Compensation rate: | Funded plans  
Disclosure of defined benefit plans [line items]  
Increase (decrease) in discount rate 10.9
Increase (decrease) in compensation rate (10.4)
Canadian | Compensation rate: | Unfunded plans  
Disclosure of defined benefit plans [line items]  
Increase (decrease) in discount rate 0.4
Increase (decrease) in compensation rate (0.4)
Foreign | Discount rate: | Funded plans  
Disclosure of defined benefit plans [line items]  
Increase (decrease) in discount rate (0.1)
Increase (decrease) in compensation rate 0.1
Foreign | Discount rate: | Unfunded plans  
Disclosure of defined benefit plans [line items]  
Increase (decrease) in discount rate (0.3)
Increase (decrease) in compensation rate 0.4
Foreign | Compensation rate: | Funded plans  
Disclosure of defined benefit plans [line items]  
Increase (decrease) in discount rate 0.0
Increase (decrease) in compensation rate 0.0
Foreign | Compensation rate: | Unfunded plans  
Disclosure of defined benefit plans [line items]  
Increase (decrease) in discount rate 0.0
Increase (decrease) in compensation rate $ 0.0