Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Statement of Income and Comprehensive Income [Abstract]
Net income	$ 479.7	$ 278.2	$ 1,233.2	$ 601.1
Other comprehensive income:
Foreign currency translation adjustments	(86.1)	48.9	(75.9)	14.4
Unrealized holding (loss) / gain on available-for-sale securities (net of taxes of $3.4 million, $0.1 million, $1.3 million and $1.2 million)	(7.2)	0.2	(3.5)	0
Comprehensive income	386.4	327.3	1,153.8	615.5
Components of accumulated other comprehensive income
Foreign currency translation adjustments	34.5		34.5		110.4
Unrealized holding loss on available-for-sale securities, net of taxes	(3.7)		(3.7)		(0.2)
Accumulated other comprehensive income	$ 30.8		$ 30.8		$ 110.2