Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Notes to Financial Statements [Abstract]
Net income	$ 164.5	$ 148.7	$ 422.1	$ 398.2
Average shares outstanding (basic) (in shares)	245,100,000	242,200,000	244,900,000	243,200,000
Common stock equivalents (in shares)	2,000,000	2,300,000	2,100,000	2,400,000
Incremental shares from assumed conversion of convertible debentures (in shares)	0	1,000,000	2,800,000	1,400,000
Diluted shares	247,100,000	245,500,000	249,800,000	247,000,000
Basic earnings per share (in hundredths)	$ 0.67	$ 0.61	$ 1.72	$ 1.64
Diluted earnings per share (in hundredths)	$ 0.67	$ 0.61	$ 1.69	$ 1.61
Interest rate percentage on Convertible Debentures included in calculation of diluted earnings per share, current period (in hundredths)	2.50%	2.50%	2.50%	2.50%
Treasury shares acquired (in shares)	0	0	0	3,176,705
Average cost of treasury shares acquired (in dollars per share)				$ 39.05
Treasury shares issued in satisfaction of stock option exercises and vesting of stock units (in shares)	132,153		1,283,827