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