Share repurchases - Schedule of Repurchase Program (Details) - CAD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2025
Share Repurchase Program [Line Items]
Amount of repurchase	$ 1,398	$ 1,773
March 2025 Normal Course Issuer Bid (NCIB)
Share Repurchase Program [Line Items]
Number of Common Shares repurchased (in shares)	12,882,454	16,363,112
Weighted-average price per share (CAD per share)	$ 108.52	$ 108.34
Amount of repurchase	$ 1,398	$ 1,773

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.

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Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Total cost of shares repurchased divided by the total number of shares repurchased.

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