Incentive Compensation Expense (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Stock-based Payment Award
Stock-based compensation expense	$ 62.4		$ 66.8		$ 62.3
Tax benefit	22.1		22.1		21.5
Stock options
Stock-based Payment Award
Stock-based compensation expense	6.7		7.4		10.2
Stock-settled awards
Stock-based Payment Award
Stock-based compensation expense	21.9		32.7		34.2
Cash-settled awards
Stock-based Payment Award
Stock-based compensation expense	5.7		10.9		9.3
Performance-based awards
Stock-based Payment Award
Stock-based compensation expense	23.3		11.0		6.4
Employee stock purchase plan
Stock-based Payment Award
Stock-based compensation expense	0.7		0.5		0.7
Other
Stock-based Payment Award
Stock-based compensation expense	4.1	[1]	4.3	[1]	1.5	[1]
Time based cash awards
Stock-based Payment Award
Incentive compensation expense, Non share-based	16.6		12.8		4.5
Performance based cash awards
Stock-based Payment Award
Incentive compensation expense, Non share-based	$ 22.0		$ 11.4		$ 3.9

[1] Represents charges recorded for severance expense related to stock-based compensation awards.