Miscellaneous financial information - Summary of Reserves and Charges (Details) - Employee Severance - CAD ($) $ in Millions |
3 Months Ended | 12 Months Ended |
|---|---|---|
Sep. 30, 2025 |
Dec. 31, 2025 |
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| Restructuring Reserve [Roll Forward] | ||
| Balance at January 1 | $ 0 | |
| Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration] | Selling and general | Selling and general |
| Additions/adjustments | $ 330 | $ 330 |
| Payments made | 0 | |
| Balance at December 31 | $ 330 |
| X | ||||||||||
- Definition Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Indicates line item in statement of income or comprehensive income that includes restructuring charges. Reference 1: http://www.xbrl.org/2003/role/recommendedDisclosureRef
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| X | ||||||||||
- Definition Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. No definition available.
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| X | ||||||||||
- Details
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