Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Statement of Income and Comprehensive Income [Abstract]
Net (loss)/income	$ (162.1)	$ 159.6	$ 256.9	$ 570.0
Other comprehensive (loss)/income:
Foreign currency translation adjustments	(220.2)	46.2	(195.5)	(83.3)
Unrealized (loss)/gain on available-for-sale securities (net of taxes benefit of $1.4 for both the three and six months ended June 30, 2016 and $nil for both the three and six months ended June 30, 2015)	(4.4)	2.6	(4.7)	3.3
Hedging activities, net of tax of $1.6 for both the three and six months ended June 30, 2016, respectively and $nil for both the three and six months ended June 30, 2015	(1.8)	0.0	(1.8)	0.0
Comprehensive (loss)/income	(388.5)	$ 208.4	54.9	$ 490.0
Components of accumulated other comprehensive income
Foreign currency translation adjustments	(377.6)		(377.6)		$ (182.1)
Unrealized holding loss on available-for-sale securities, net of taxes	(6.4)		(6.4)		(1.7)
Hedging activities, net of taxes	(1.8)		(1.8)		0.0
Accumulated other comprehensive loss	$ (385.8)		$ (385.8)		$ (183.8)