CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Millions		Total	Capital stock	Treasury stock	Additional paid-in capital	Retained earnings (accumulated deficit)	Accumulated other comprehensive income (loss)
Beginning balance at Dec. 31, 2023		$ 1,771.0	$ 1,672.5	$ (80.1)	$ 1,030.6	$ (851.8)	$ (0.2)	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of capital stock		3.9	5.6		(1.7)
Repurchase of capital stock for cancellation	[2]	(126.1)	(41.1)		(85.0)
Purchase of treasury stock for SBC plans	[3]	(94.1)		(94.1)
SBC cash settlement		(69.0)			(69.0)
Stock-based compensation (SBC)		48.7		86.7	(38.0)
Net earnings for the period		276.3				276.3
Other comprehensive (loss) income		3.4					3.4	[1]
Ending balance at Sep. 30, 2024		1,814.1	1,637.0	(87.5)	836.9	(575.5)	3.2	[1]
Beginning balance at Jun. 30, 2024		1,798.6	1,668.5	(92.5)	899.5	(665.0)	(11.9)	[1]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of capital stock		0.0	0.2		(0.2)
Repurchase of capital stock for cancellation	[4]	(102.3)	(31.7)		(70.6)
Stock-based compensation (SBC)		13.2		5.0	8.2
Net earnings for the period		89.5				89.5
Other comprehensive (loss) income		15.1					15.1	[1]
Ending balance at Sep. 30, 2024		1,814.1	1,637.0	(87.5)	836.9	(575.5)	3.2	[1]
Beginning balance at Dec. 31, 2024		1,896.0	1,632.8	(92.9)	797.5	(423.8)	(17.6)	[5]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of capital stock		0.3	6.0		(5.7)
Repurchase of capital stock for cancellation	[6]	(116.9)	(17.2)		(99.7)
Purchase of treasury stock for SBC plans		(221.6)		(221.6)
SBC cash settlement		(156.0)			(156.0)
Stock-based compensation (SBC)		57.7		113.5	(55.8)
Net earnings for the period		565.0				565.0
Other comprehensive (loss) income		4.1					4.1	[5]
Ending balance at Sep. 30, 2025		2,028.6	1,621.6	(201.0)	480.3	141.2	(13.5)	[5]
Beginning balance at Jun. 30, 2025		1,757.9	1,621.5	(202.2)	466.1	(126.6)	(0.9)	[5]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of capital stock		0.0	0.1		(0.1)
Stock-based compensation (SBC)		15.5		1.2	14.3
Net earnings for the period		267.8				267.8
Other comprehensive (loss) income		(12.6)					(12.6)	[5]
Ending balance at Sep. 30, 2025		$ 2,028.6	$ 1,621.6	$ (201.0)	$ 480.3	$ 141.2	$ (13.5)	[5]

[1] Accumulated other comprehensive income (loss) is net of tax (see note 10).

[2] Consists of $126.5 paid to repurchase common shares for cancellation during the first nine months of 2024 and accrued share buyback taxes, offset in part by the reversal of $2.7 accrued at December 31, 2023 for the estimated contractual maximum quantity of permitted common share repurchases (Contractual Maximum Quantity) under an automatic share purchase plan (ASPP) executed in December 2023 for such purpose (see note 9).

[3] Consists of $101.6 paid to repurchase common shares for delivery obligations under our SBC plans during the first nine months of 2024, offset in part by the reversal of $7.5 accrued at December 31, 2023 for the estimated Contractual Maximum Quantity under an ASPP executed in September 2023 for such purpose (see note 9).

[4] Consists of $100.0 paid to repurchase common shares for cancellation during the third quarter of 2024 and accrued share buyback taxes (see note 9).

[5] Accumulated other comprehensive income (loss) is net of tax (see note 10).

[6] Consists of $115.0 paid to repurchase common shares for cancellation during the first nine months of 2025 and accrued share buyback taxes (see note 9).