Share Repurchases (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Summarize details of share repurchase activity
Number of shares	3.3	3.5	0.2
Weighted average price per share	$ 37.16	$ 44.02	$ 30.55
Amount Repurchased	$ 123.0	$ 153.7	$ 5.6
Share Repurchases (Textual) [Abstract]
Amount for repurchase of shares of common stock				300.0
Increased amount for repurchase of shares of common stock	100.0
Related to Share-Based Payments [Member]
Summarize details of share repurchase activity
Number of shares	0.1	0.2	0.2
Weighted average price per share	$ 39.26	$ 44.83	$ 30.55
Amount Repurchased	3.3	9.4	5.6
2008 Plan [Member]
Summarize details of share repurchase activity
Number of shares	3.2	3.3
Weighted average price per share	$ 37.11	$ 43.97
Amount Repurchased	$ 119.7	$ 144.3