Condensed Consolidated Statements of Changes in Equity - USD ($) shares in Millions, $ in Millions	Total	Ordinary shares	Additional paid-in capital	Retained earnings	Accumulated other comprehensive loss
Dividends (in dollars per share)	$ 0.19
Beginning Balance at Dec. 31, 2019	$ 1,953.9	$ 1.7	$ 1,777.7	$ 401.0	$ (226.5)
Beginning Balance (in shares) at Dec. 31, 2019		168.3
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	72.7			72.7
Other comprehensive loss, net of tax	1.3				1.3
Dividends declared	(31.6)			(31.6)
Share repurchase (in shares)		(3.0)
Share repurchases	(115.2)		(115.2)
Exercise of options, net of shares tendered for payment	8.8		8.8
Exercise of options, net of shares tendered for payment (in shares)		0.3
Issuance of restricted shares, net of cancellations (in shares)		0.2
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	(3.6)		(3.6)
Share-based compensation	6.2		6.2
Ending Balance (in shares) at Mar. 31, 2020		165.7
Ending Balance at Mar. 31, 2020	$ 1,892.5	$ 1.7	1,673.9	442.1	(225.2)
Dividends (in dollars per share)	$ 0.20
Beginning Balance at Dec. 31, 2020	$ 2,106.3	$ 1.7	1,680.7	631.2	(207.3)
Beginning Balance (in shares) at Dec. 31, 2020		166.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	128.6			128.6
Other comprehensive loss, net of tax	(3.7)				(3.7)
Dividends declared	(33.3)			(33.3)
Share repurchase (in shares)		(0.2)
Share repurchases	(9.6)		(9.6)
Exercise of options, net of shares tendered for payment	5.2		5.2
Exercise of options, net of shares tendered for payment (in shares)		0.1
Issuance of restricted shares, net of cancellations (in shares)		0.2
Issuance of restricted shares, net of cancellations	0.0
Shares surrendered by employees to pay taxes (in shares)		0.0
Shares surrendered by employees to pay taxes	(5.3)		(5.3)
Share-based compensation	5.6		5.6
Ending Balance (in shares) at Mar. 31, 2021		166.2
Ending Balance at Mar. 31, 2021	$ 2,193.8	$ 1.7	$ 1,676.6	$ 726.5	$ (211.0)