Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income/(loss)	$ 240.3	$ (162.1)	$ 615.3	$ 256.9
Other comprehensive income/(loss):
Foreign currency translation adjustments	1,431.0	(220.2)	1,696.5	(195.5)
Pension and other employee benefits (net of tax expense of $1.3 and $0.9 for the three and six months ended June 30, 2017 and $nil for both the three and six months ended June 30, 2016)	3.2	0.0	10.6	0.0
Unrealized loss on available-for-sale securities (net of tax benefit of $0.5 and tax expense of $1.7 for the three and six months ended June 30, 2017 and tax benefit of $1.4 for both the three and six months ended June 30, 2016)	(5.6)	(4.4)	(3.5)	(4.7)
Hedging activities (net of tax benefit of $0.5 and $3.2 for the three and six months ended June 30, 2017 and $1.6 for both the three and six months ended June 30, 2016)	(1.4)	(1.8)	(5.9)	(1.8)
Comprehensive income/(loss)	1,667.5	$ (388.5)	2,313.0	$ 54.9
Components of accumulated other comprehensive loss
Foreign currency translation adjustments	191.1		191.1		$ (1,505.4)
Pension and other employee benefits, net of taxes	5.4		5.4		(5.2)
Unrealized holding gain on available-for-sale securities, net of taxes	3.1		3.1		6.6
Hedging activities, net of taxes	0.5		0.5		6.4
Accumulated other comprehensive income/(loss)	$ 200.1		$ 200.1		$ (1,497.6)