Leases - Present Value of Minimum Lease Payments (Details) - CAD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Operating Leases
2025	$ 18
2026	15
2027	12
2028	6
2029	4
Thereafter	19
Total operating lease payments	74
Less: Imputed interest	(10)
Total lease obligations	64
Less: Current installments	(17)	$ (12)
Other liabilities	47	39
Finance Leases
2025	37
2026	37
2027	37
2028	37
2029	37
Thereafter	954
Total finance lease payments	1,139
Less: Imputed interest	(792)
Total lease obligations	347
Less: Current installments	(4)	(3)
Finance leases	343	$ 339
Total
2025	55
2026	52
2027	49
2028	43
2029	41
Thereafter	973
Total lease payments	1,213
Less: Imputed interest	(802)
Total lease obligations	411
Less: Current installments	(21)
Long-term lease obligations	$ 390

Finance Lease and Lessee, Operating Lease, Liability, Current

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Finance Lease and Lessee, Operating Lease, Liability, Noncurrent

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Finance Lease and Lessee, Operating Lease, Liability, Payments, Due

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Finance Lease and Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months

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Finance Lease and Lessee, Operating Lease, Liability, Payments, Due Year Five

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Finance Lease and Lessee, Operating Lease, Liability, Payments, Due Year Four

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Finance Lease and Lessee, Operating Lease, Liability, Payments, Due Year Three

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Finance Lease and Lessee, Operating Lease, Liability, Payments, Due Year Two

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Finance Lease and Lessee, Operating Lease, Liability, Payments, Due after Year Five

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Finance Lease and Lessee, Operating Lease, Liability, Total

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Finance Lease and Lessee, Operating Lease, Liability, Undiscounted Excess Amount

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Finance Lease and Operating Lease Liabilities, Payments Due [Abstract]

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Present value of lessee's discounted obligation for lease payments from finance lease.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478964/842-20-50-6

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

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Present value of lessee's discounted obligation for lease payments from finance lease, classified as current.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 842
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479041/842-20-45-1

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Present value of lessee's discounted obligation for lease payments from finance lease, classified as noncurrent.

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Amount of lessee's undiscounted obligation for lease payments for finance lease.

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Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for finance lease.

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Amount of lessee's undiscounted obligation for lease payment for operating lease.

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Amount of lessee's undiscounted obligation for lease payment for operating lease due after fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for operating lease.

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Present value of lessee's discounted obligation for lease payments from operating lease.

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

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Present value of lessee's discounted obligation for lease payments from operating lease, classified as noncurrent.

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