CAPITAL STOCK - Schedule of Common Shares Purchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Aggregate cost (including transaction fees and excluding share buyback taxes) of Common Shares repurchased for cancellation	$ 0.0	$ 100.0	$ 115.0	$ 126.5
Number of common shares repurchased for cancellation (in shares)	0.0	2.2	1.2	2.9
Weighted average price per share for repurchases (in dollars per share)	$ 0	$ 44.44	$ 94.05	$ 43.28
Aggregate cost (including transaction fees) of Common Shares repurchased for delivery under SBC plans	$ 0.0	$ 0.0	$ 221.6	$ 101.6
Number of Common Shares repurchased for delivery under SBC plans (in shares)	0.0	0.0	1.7	2.8
NCIB ASPP
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of common shares repurchased for cancellation (in shares)	0.0	0.0	0.6	0.5

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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+ Details

- Definition

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.

+ References + Details