Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Statement of Income and Comprehensive Income [Abstract]
Net income	$ 237.8	$ 205.5	$ 476.2	$ 416.8
Other comprehensive income:
Foreign currency translation adjustments	(54.3)	29.6	(17.7)	100.2
Unrealized holding gain on available-for-sale securities (net of taxes of $2.9 million, $1.1 million, $2.9 million and $3.4 million)	3.1	5.9	6.0	16.0
Other than temporary impairment of available-for-sale securities (net of taxes of $nil in all periods)	0	0	0	2.4
Comprehensive income	186.6	241.0	464.5	535.4
Components of accumulated other comprehensive income
Foreign currency translation adjustments	43.7		43.7		61.4
Unrealized holding gain/(loss) on available-for-sale securities, net of taxes	4.9		4.9		(1.1)
Accumulated other comprehensive income	$ 48.6		$ 48.6		$ 60.3