Stockholders' Equity (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Total Share-based Compensation expense
Total share-based incentive compensation expense	$ 12.3	$ 10.5
2012 Three-year PSU Awards [Member]
Total Share-based Compensation expense
Total share-based incentive compensation expense	0.7
2011 Three-year PSU Awards [Member]
Total Share-based Compensation expense
Total share-based incentive compensation expense	0.3	0.9
2010 Three-year PSU Awards [Member]
Total Share-based Compensation expense
Total share-based incentive compensation expense	(0.4)	0.8
2009 Three-year PSU Awards [Member]
Total Share-based Compensation expense
Total share-based incentive compensation expense		1.5
2012 CEO Incentive Compensation [Member]
Total Share-based Compensation expense
Total share-based incentive compensation expense	1.4
SLO Awards [Member]
Total Share-based Compensation expense
Total share-based incentive compensation expense	0.3	0.4
Other long-term share-based incentive compensation programs [Member]
Total Share-based Compensation expense
Total share-based incentive compensation expense	$ 2.3	$ 2.2