Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Statement of Income and Comprehensive Income [Abstract]
Net income	$ 278.2	$ 227.2	$ 601.1	$ 703.4
Other comprehensive income:
Foreign currency translation adjustments	48.9	22.7	14.4	5.0
Unrealized holding gain/(loss) on available-for-sale securities (net of taxes of $0.1 million, $0.8 million, $1.2 million and $3.7 million)	0.2	1.2		7.2
Comprehensive income	327.3	251.1	615.5	715.6
Components of accumulated other comprehensive income
Foreign currency translation adjustments	99.5		99.5		85.1
Unrealized holding gain/(loss) on available-for-sale securities, net of taxes	1.8		1.8		1.8
Accumulated other comprehensive income	$ 101.3		$ 101.3		$ 86.9