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
Cash dividends declared per ordinary share	$ 0.18
Beginning Balance (in shares) at Dec. 31, 2018		171.4
Beginning Balance at Dec. 31, 2018	$ 1,836.1	$ 1.7	$ 1,893.8	$ 169.2	$ (228.6)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	51.3			51.3
Other comprehensive income, net of tax	2.7				2.7
Dividends declared	(31.0)			(31.0)
Exercise of options, net of shares tendered for payment (in shares)		0.3
Exercise of options, net of shares tendered for payment	9.1		9.1
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	(3.2)		(3.2)
Share-based compensation	5.4		5.4
Ending Balance (in shares) at Mar. 31, 2019		171.9
Ending Balance at Mar. 31, 2019	$ 1,870.4	$ 1.7	1,905.1	189.5	(225.9)
Cash dividends declared per ordinary 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 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)