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
Beginning Balance at Dec. 31, 2015	$ 4,008.8	$ 1.8	$ 2,860.3	$ 1,791.7	$ (645.0)
Beginning Balance (in shares) at Dec. 31, 2015		180.5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	250.2			250.2
Other comprehensive loss, net of tax	(1.6)				(1.6)
Dividends declared	(121.7)			(121.7)
Exercise of options, net of shares tendered for payment	13.8		13.8
Exercise of options, net of shares tendered for payment (in shares)		0.4
Issuance of restricted shares, net of cancellations (in shares)		0.3
Shares surrendered by employees to pay taxes	(5.5)		(5.5)
Shares surrendered by employees to pay taxes (in shares)		(0.1)
Share-based compensation	22.3		22.3
Ending Balance (in shares) at Jun. 30, 2016		181.1
Ending Balance at Jun. 30, 2016	4,166.3	$ 1.8	2,890.9	1,920.2	(646.6)
Beginning Balance at Dec. 31, 2016	4,254.4	$ 1.8	2,920.8	2,068.1	(736.3)
Beginning Balance (in shares) at Dec. 31, 2016		181.8
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	351.5			351.5
Other comprehensive loss, net of tax	469.0				469.0
Dividends declared	(126.9)			(126.9)
Stock Repurchased During Period, Value	(100.0)		(100.0)
Stock Repurchased During Period, Shares		(1.5)
Exercise of options, net of shares tendered for payment	36.5		36.5
Exercise of options, net of shares tendered for payment (in shares)		1.0
Issuance of restricted shares, net of cancellations	0.0
Issuance of restricted shares, net of cancellations (in shares)		0.3
Shares surrendered by employees to pay taxes	(7.0)		(7.0)
Shares surrendered by employees to pay taxes (in shares)		(0.1)
Share-based compensation	26.0		26.0
Ending Balance (in shares) at Jun. 30, 2017		181.5
Ending Balance at Jun. 30, 2017	$ 4,903.5	$ 1.8	$ 2,876.3	$ 2,292.7	$ (267.3)