Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Statement of Income and Comprehensive Income [Abstract]
Net income	$ 258.1	$ 237.8	$ 322.9	$ 476.2
Other comprehensive income:
Foreign currency translation adjustments	1.6	(54.3)	(34.5)	(17.7)
Unrealized holding gain/(loss) on available-for-sale securities (net of taxes of $0.9 million, $2.9 million, $1.1 million and $2.9 million)	1.5	3.1	(0.2)	6.0
Comprehensive income	261.2	186.6	288.2	464.5
Components of accumulated other comprehensive income
Foreign currency translation adjustments	50.6		50.6		85.1
Unrealized holding gain/(loss) on available-for-sale securities, net of taxes	1.6		1.6		1.8
Accumulated other comprehensive income	$ 52.2		$ 52.2		$ 86.9