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	391.2			391.2
Other comprehensive income, net of tax	28.5				28.5
Dividends declared	(122.0)			(122.0)
Exercise of options, net of shares tendered for payment	30.7		30.7
Exercise of options, net of shares tendered for payment (in shares)		0.9
Issuance of restricted shares, net of cancellations (in shares)		0.5
Shares surrendered by employees to pay taxes	(10.6)		(10.6)
Shares surrendered by employees to pay taxes (in shares)		(0.2)
Share-based compensation	28.7		28.7
Ending Balance (in shares) at Sep. 30, 2016		181.7
Ending Balance at Sep. 30, 2016	4,355.3	$ 1.8	2,909.1	2,060.9	(616.5)
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	476.9			476.9
Other comprehensive income, net of tax	500.5				500.5
Dividends declared	(189.7)			(189.7)
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	41.6		41.6
Exercise of options, net of shares tendered for payment (in shares)		1.1
Issuance of restricted shares, net of cancellations (in shares)		0.3
Shares surrendered by employees to pay taxes	(7.3)		(7.3)
Shares surrendered by employees to pay taxes (in shares)		(0.1)
Share-based compensation	32.2		32.2
Ending Balance (in shares) at Sep. 30, 2017		181.6
Ending Balance at Sep. 30, 2017	$ 5,008.6	$ 1.8	$ 2,887.3	$ 2,355.3	$ (235.8)