Net Income Per Common Share (Details) (USD $) In Millions	3 Months Ended			9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2008	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2009
Basic:
Income from continuing operations	$ 160.2	$ 141.7		$ 477.4	$ 301.9
Income from discontinued operations			16.6	190.3		25.5
Net income applicable to common stock	160.2	141.7		667.7	301.9
Weighted average common shares outstanding	162.3	165.3		164.3	166.9
Diluted:
Income from continuing operations	160.2	141.7		477.4	301.9
Income from discontinued operations			16.6	190.3		25.5
Net income applicable to common stock	$ 160.2	$ 141.7		$ 667.7	$ 301.9
Weighted average common shares outstanding	162.3	165.3		164.3	166.9
Incremental shares from assumed conversions:
Options, performance-based stock awards and other employee awards	1.7	1.8		2.2	1.9
Weighted average common shares and common share equivalents	164.0	167.1		166.5	168.8