Major commitments and contingencies (Guarantees and Indemnifications) (Details) - CAD ($)	Dec. 31, 2025	Dec. 31, 2024
Guarantee Obligations
Guarantees and indemnifications
Liability current carrying value	$ 0
Indemnification Agreement
Guarantees and indemnifications
Liability current carrying value	0
Performance Guarantee \| Committed Bilateral Letter of Credit Facilites
Guarantees and indemnifications
Outstanding letters of credit	321,000,000	$ 329,000,000
Maximum potential liability under guarantees	621,000,000	616,000,000
Performance Guarantee \| Uncommitted Bilateral Letter of Credit Facilities
Guarantees and indemnifications
Outstanding letters of credit	153,000,000	142,000,000
Performance Guarantee \| Surety and Other Bond
Guarantees and indemnifications
Liability current carrying value	147,000,000	145,000,000
Other Employee Benefit Liabilities and Workers' Compensation
Guarantees and indemnifications
Maximum potential liability under guarantees	580,000,000	571,000,000
Other Liabilities
Guarantees and indemnifications
Maximum potential liability under guarantees	$ 41,000,000	$ 45,000,000

No definition available.

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- Definition

The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

+ Details

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- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482425/460-10-50-4

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477548/944-605-55-15

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477548/944-605-55-12

+ Details

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