v3.26.1
FINANCIAL RISK MANAGEMENT - Maturity Analysis (Details) - CAD ($)
$ in Millions
Mar. 31, 2026
Mar. 31, 2025
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Carrying amount $ 4,006.7 $ 4,476.2
Contractual cash flows 5,069.8 5,671.3
Derivative financial instruments, carrying amount 28.8 39.7
Derivative financial instruments, undiscounted cash flows 49.8 72.3
Non-derivative financial liabilities and derivative financial instruments, carrying amount 4,035.5 4,515.9
Non-derivative financial liabilities and derivative financial instruments, undiscounted cash flows 5,119.6 5,743.6
Less than 1 year    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 1,082.8 1,456.2
Derivative financial instruments, undiscounted cash flows 21.8 26.1
Non-derivative financial liabilities and derivative financial instruments, undiscounted cash flows 1,104.6 1,482.3
Between 1 and 2 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 675.8 667.8
Derivative financial instruments, undiscounted cash flows 9.9 11.9
Non-derivative financial liabilities and derivative financial instruments, undiscounted cash flows 685.7 679.7
Between 2 and 3 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 843.8 329.8
Derivative financial instruments, undiscounted cash flows 18.1 2.8
Non-derivative financial liabilities and derivative financial instruments, undiscounted cash flows 861.9 332.6
Between 3 and 4 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 262.7 834.4
Derivative financial instruments, undiscounted cash flows 0.0 31.5
Non-derivative financial liabilities and derivative financial instruments, undiscounted cash flows 262.7 865.9
Between 4 and 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 417.9 250.2
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Non-derivative financial liabilities and derivative financial instruments, undiscounted cash flows 417.9 250.2
More than 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 1,786.8 2,132.9
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Non-derivative financial liabilities and derivative financial instruments, undiscounted cash flows 1,786.8 2,132.9
Forward foreign currency contracts    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, carrying amount 19.8 38.3
Outflow    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 2,402.8 2,829.3
Outflow | Less than 1 year    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 2,084.5 2,481.4
Outflow | Between 1 and 2 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 307.6 305.6
Outflow | Between 2 and 3 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 10.7 39.4
Outflow | Between 3 and 4 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 2.9
Outflow | Between 4 and 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Outflow | More than 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Inflow    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows (2,372.2) (2,780.2)
Inflow | Less than 1 year    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows (2,062.7) (2,443.3)
Inflow | Between 1 and 2 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows (298.9) (295.4)
Inflow | Between 2 and 3 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows (10.6) (38.5)
Inflow | Between 3 and 4 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 (3.0)
Inflow | Between 4 and 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Inflow | More than 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Foreign currency and interest rate swap agreements    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, carrying amount 10.0 14.4
Derivative financial instruments, undiscounted cash flows 20.2 36.2
Foreign currency and interest rate swap agreements | Less than 1 year    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 1.0 1.0
Foreign currency and interest rate swap agreements | Between 1 and 2 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 1.2 1.7
Foreign currency and interest rate swap agreements | Between 2 and 3 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 18.0 1.9
Foreign currency and interest rate swap agreements | Between 3 and 4 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 31.6
Foreign currency and interest rate swap agreements | Between 4 and 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Foreign currency and interest rate swap agreements | More than 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Equity swap agreements    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, carrying amount (1.0) (13.0)
Derivative financial instruments, undiscounted cash flows (1.0) (13.0)
Equity swap agreements | Less than 1 year    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows (1.0) (13.0)
Equity swap agreements | Between 1 and 2 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Equity swap agreements | Between 2 and 3 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Equity swap agreements | Between 3 and 4 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Equity swap agreements | Between 4 and 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Equity swap agreements | More than 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Derivative financial instruments, undiscounted cash flows 0.0 0.0
Accounts payable and accrued liabilities    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Carrying amount 699.9 914.4
Contractual cash flows 699.9 914.4
Accounts payable and accrued liabilities | Less than 1 year    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 699.9 914.4
Accounts payable and accrued liabilities | Between 1 and 2 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 0.0 0.0
Accounts payable and accrued liabilities | Between 2 and 3 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 0.0 0.0
Accounts payable and accrued liabilities | Between 3 and 4 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 0.0 0.0
Accounts payable and accrued liabilities | Between 4 and 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 0.0 0.0
Accounts payable and accrued liabilities | More than 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 0.0 0.0
Long-term debt (other than lease liabilities)    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Carrying amount 2,472.0 2,678.3
Contractual cash flows 2,472.0 2,678.3
Long-term debt (other than lease liabilities) | Less than 1 year    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 183.9 277.9
Long-term debt (other than lease liabilities) | Between 1 and 2 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 476.3 469.3
Long-term debt (other than lease liabilities) | Between 2 and 3 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 653.0 140.6
Long-term debt (other than lease liabilities) | Between 3 and 4 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 123.2 654.5
Long-term debt (other than lease liabilities) | Between 4 and 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 235.8 121.7
Long-term debt (other than lease liabilities) | More than 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 799.8 1,014.3
Interest and accretion    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Carrying amount 0.0 0.0
Contractual cash flows 602.1 686.2
Interest and accretion | Less than 1 year    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 86.7 93.2
Interest and accretion | Between 1 and 2 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 72.2 74.6
Interest and accretion | Between 2 and 3 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 49.6 67.5
Interest and accretion | Between 3 and 4 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 35.3 50.0
Interest and accretion | Between 4 and 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 49.3 34.7
Interest and accretion | More than 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 309.0 366.2
Lease liabilities    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Carrying amount 762.2 792.1
Contractual cash flows 1,173.7 1,237.2
Lease liabilities | Less than 1 year    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 112.3 170.7
Lease liabilities | Between 1 and 2 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 103.2 98.9
Lease liabilities | Between 2 and 3 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 113.4 90.3
Lease liabilities | Between 3 and 4 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 82.0 101.8
Lease liabilities | Between 4 and 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 110.9 69.9
Lease liabilities | More than 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 651.9 705.6
Other non-current liabilities    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Carrying amount 72.6 91.4
Contractual cash flows 122.1 155.2
Other non-current liabilities | Less than 1 year    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 0.0 0.0
Other non-current liabilities | Between 1 and 2 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 24.1 25.0
Other non-current liabilities | Between 2 and 3 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 27.8 31.4
Other non-current liabilities | Between 3 and 4 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 22.2 28.1
Other non-current liabilities | Between 4 and 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows 21.9 23.9
Other non-current liabilities | More than 5 years    
Disclosure of maturity analysis for non-derivative financial liabilities [line items]    
Contractual cash flows $ 26.1 $ 46.8