Stockholders' Equity (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Total Share-based incentive compensation expense
Total share-based incentive compensation expense	$ 5.7	$ 7.4	$ 10.3	$ 13.2
2012 Three-year PSU Awards [Member]
Total Share-based incentive compensation expense
Total share-based incentive compensation expense	0.7		1.4
2011 Three-year PSU Awards [Member]
Total Share-based incentive compensation expense
Total share-based incentive compensation expense	0.5	0.9	0.8	1.8
2010 Three-year PSU Awards [Member]
Total Share-based incentive compensation expense
Total share-based incentive compensation expense	0.7	3.0	0.3	3.8
2009 Three-year PSU Awards [Member]
Total Share-based incentive compensation expense
Total share-based incentive compensation expense		0.9		2.4
2012 CEO Incentive Compensation [Member]
Total Share-based incentive compensation expense
Total share-based incentive compensation expense	0.9		2.3
SLO Awards [Member]
Total Share-based incentive compensation expense
Total share-based incentive compensation expense	0.1	0.2	0.4	0.6
Other long-term share-based incentive compensation programs [Member]
Total Share-based incentive compensation expense
Total share-based incentive compensation expense	$ 2.8	$ 2.4	$ 5.1	$ 4.6