Consolidated Statements of Changes In Equity - USD ($) shares in Millions, $ in Millions	Total	Common shares	Capital contribution reserve	Retained earnings	Accumulated other comprehensive income (loss)
Balance (in shares) at Dec. 31, 2020		166.1
Beginning Balance at Dec. 31, 2020	$ 2,106.3	$ 1.7	$ 1,680.7	$ 631.2	$ (207.3)
Net income	553.0			553.0
Other comprehensive loss, net of tax	(6.6)				(6.6)
Dividends declared	(132.8)			(132.8)
Share repurchase (in shares)		(2.1)
Share repurchases	(150.0)		(150.0)
Exercise of options, net of shares tendered for payment (in shares)		0.9
Exercise of options, net of shares tendered for payment	30.1		30.1
Issuance of restricted shares, net of cancellations (in shares)		0.3
Issuance of restricted shares, net of cancellations	0.0
Shares surrendered by employees to pay taxes (in shares)		(0.1)
Shares surrendered by employees to pay taxes	(7.9)		(7.9)
Share-based compensation	29.8		29.8
Balance (in shares) at Dec. 31, 2021		165.1
Ending Balance at Dec. 31, 2021	2,421.9	$ 1.7	1,582.7	1,051.4	(213.9)
Net income	480.9			480.9
Other comprehensive loss, net of tax	(25.1)				(25.1)
Dividends declared	(141.8)			(141.8)
Share repurchase (in shares)		(1.0)
Share repurchases	(50.0)		(50.0)
Exercise of options, net of shares tendered for payment (in shares)		0.1
Exercise of options, net of shares tendered for payment	3.6		3.6
Issuance of restricted shares, net of cancellations (in shares)		0.4
Issuance of restricted shares, net of cancellations	0.0
Shares surrendered by employees to pay taxes (in shares)		(0.1)
Shares surrendered by employees to pay taxes	(6.3)		(6.3)
Share-based compensation	24.9		24.9
Balance (in shares) at Dec. 31, 2022		164.5
Ending Balance at Dec. 31, 2022	2,708.1	$ 1.7	1,554.9	1,390.5	(239.0)
Net income	622.7			622.7
Other comprehensive loss, net of tax	(5.4)				(5.4)
Dividends declared	$ (147.0)			(147.0)
Exercise of options, net of shares tendered for payment (in shares)	0.3	0.4
Exercise of options, net of shares tendered for payment	$ 18.3		18.3
Issuance of restricted shares, net of cancellations (in shares)		0.5
Issuance of restricted shares, net of cancellations	0.0
Shares surrendered by employees to pay taxes (in shares)		(0.1)
Shares surrendered by employees to pay taxes	(8.7)		(8.7)
Share-based compensation	29.1		29.1
Balance (in shares) at Dec. 31, 2023		165.3
Ending Balance at Dec. 31, 2023	$ 3,217.1	$ 1.7	$ 1,593.6	$ 1,866.2	$ (244.4)