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 (in shares) at Dec. 31, 2019		168.3
Beginning Balance at Dec. 31, 2019	$ 1,953.9	$ 1.7	$ 1,777.7	$ 401.0	$ (226.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	72.7			72.7
Other comprehensive income, 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 (in shares)		0.3
Exercise of options, net of shares tendered for payment	8.8		8.8
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)
Beginning Balance (in shares) at Dec. 31, 2019		168.3
Beginning Balance at Dec. 31, 2019	1,953.9	$ 1.7	1,777.7	401.0	(226.5)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	255.6
Ending Balance (in shares) at Sep. 30, 2020		166.3
Ending Balance at Sep. 30, 2020	$ 2,049.8	$ 1.7	1,698.8	561.6	(212.3)
Dividends (in dollars per share)	$ 0.19
Beginning Balance (in shares) at Mar. 31, 2020		165.7
Beginning Balance at Mar. 31, 2020	$ 1,892.5	$ 1.7	1,673.9	442.1	(225.2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	72.1			72.1
Other comprehensive income, net of tax	10.4				10.4
Dividends declared	(31.7)			(31.7)
Exercise of options, net of shares tendered for payment (in shares)		0.1
Exercise of options, net of shares tendered for payment	2.8		2.8
Issuance of restricted shares, net of cancellations (in shares)		0.1
Issuance of restricted shares, net of cancellations	0.0
Shares surrendered by employees to pay taxes	(0.6)		(0.6)
Share-based compensation	4.2		4.2
Ending Balance (in shares) at Jun. 30, 2020		165.9
Ending Balance at Jun. 30, 2020	$ 1,949.7	$ 1.7	1,680.3	482.5	(214.8)
Dividends (in dollars per share)	$ 0.19
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 110.8			110.8
Other comprehensive income, net of tax	2.5				2.5
Dividends declared	(31.7)			(31.7)
Exercise of options, net of shares tendered for payment (in shares)		0.4
Exercise of options, net of shares tendered for payment	14.1		14.1
Shares surrendered by employees to pay taxes	(0.4)		(0.4)
Share-based compensation	4.8		4.8
Ending Balance (in shares) at Sep. 30, 2020		166.3
Ending Balance at Sep. 30, 2020	$ 2,049.8	$ 1.7	1,698.8	561.6	(212.3)
Dividends (in dollars per share)	$ 0.20
Beginning 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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	128.6			128.6
Other comprehensive income, 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 (in shares)		0.1
Exercise of options, net of shares tendered for payment	5.2		5.2
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	(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)
Beginning 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)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 404.3
Share repurchase (in shares)	(1.4)
Share repurchases	$ (100.0)
Ending Balance (in shares) at Sep. 30, 2021		165.5
Ending Balance at Sep. 30, 2021	$ 2,338.1	$ 1.7	1,614.2	935.8	(213.6)
Dividends (in dollars per share)	$ 0.20
Beginning Balance (in shares) at Mar. 31, 2021		166.2
Beginning Balance at Mar. 31, 2021	$ 2,193.8	$ 1.7	1,676.6	726.5	(211.0)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	132.1			132.1
Other comprehensive income, net of tax	4.3				4.3
Dividends declared	(33.3)			(33.3)
Share repurchase (in shares)		(0.6)
Share repurchases	(40.4)		(40.4)
Exercise of options, net of shares tendered for payment (in shares)		0.3
Exercise of options, net of shares tendered for payment	5.6		5.6
Issuance of restricted shares, net of cancellations (in shares)		0.1
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	(1.5)		(1.5)
Share-based compensation	11.0		11.0
Ending Balance (in shares) at Jun. 30, 2021		165.9
Ending Balance at Jun. 30, 2021	$ 2,271.6	$ 1.7	1,651.3	825.3	(206.7)
Dividends (in dollars per share)	$ 0.20
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 143.6			143.6
Other comprehensive income, net of tax	(6.9)				(6.9)
Dividends declared	(33.1)			(33.1)
Share repurchase (in shares)		(0.6)
Share repurchases	(50.0)		(50.0)
Exercise of options, net of shares tendered for payment (in shares)		0.2
Exercise of options, net of shares tendered for payment	8.9		8.9
Shares surrendered by employees to pay taxes (in shares)		0.0
Shares surrendered by employees to pay taxes	(0.2)		(0.2)
Share-based compensation	4.2		4.2
Ending Balance (in shares) at Sep. 30, 2021		165.5
Ending Balance at Sep. 30, 2021	$ 2,338.1	$ 1.7	$ 1,614.2	$ 935.8	$ (213.6)