Net Income Per Common Share (Detail) (USD $) In Millions, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Numerator
Net Income	$ 229.8	$ 209.7	$ 455.2	$ 439.5
Denominator (000s)
Weighted Average Common Shares - Basic	306,316,200	331,236,800	309,513,000	331,752,600
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	1,094,800	1,395,400	1,342,400	1,324,900
Weighted Average Common Shares - Assuming Dilution	307,411,000	332,632,000	310,855,000	333,078,000
Net Income Per Common Share
Basic	$ 0.75	$ 0.63	$ 1.47	$ 1.32
Assuming Dilution	$ 0.75	$ 0.63	$ 1.46	$ 1.32