Share repurchases - Narrative (Details) - March 2025 Normal Course Issuer Bid (NCIB) - CAD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2025	Mar. 03, 2025
Share Repurchase Program [Line Items]
Common Shares authorized to be repurchased			37.3
Share repurchase program, change in accrued tax liability	$ 37	$ 70

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 505
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481520/505-30-50-4

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