Net Income Per Common Share (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator
Net Income	$ 221.1	$ 205.7	$ 692.5	$ 636.9
Denominator (000s)
Weighted Average Common Shares - Basic	253,586,100	262,945,900	256,573,600	265,932,600
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	1,209,400	1,314,100	1,210,100	1,161,100
Weighted Average Common Shares - Assuming Dilution	254,795,500	264,260,000	257,783,700	267,093,700
Net Income Per Common Share
Basic	$ 0.87	$ 0.78	$ 2.70	$ 2.39
Assuming Dilution	$ 0.87	$ 0.78	$ 2.69	$ 2.38