Leases - Present Value of Minimum Lease Payments (Details) - CAD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Operating Leases
2024	$ 14
2025	11
2026	10
2027	6
2028	3
Thereafter	16
Total operating lease payments	60
Less: Imputed interest	(9)
Total lease obligations	51
Less: Current installments	(12)	$ (9)
Other liabilities	39	34
Finance Leases
2024	36
2025	36
2026	36
2027	36
2028	36
Thereafter	978
Total finance lease payments	1,158
Less: Imputed interest	(816)
Total lease obligations	342
Less: Current installments	(3)	(2)
Finance leases	339	$ 336
Total
2024	50
2025	47
2026	46
2027	42
2028	39
Thereafter	994
Total lease payments	1,218
Less: Imputed interest	(825)
Total lease obligations	393
Less: Current installments	(15)
Long-term lease obligations	$ 378

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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