Net Income Per Common Share (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Numerator
Net Income	$ 228.9	$ 212.6
Denominator (000s)
Weighted Average Number of Shares Outstanding, Basic	259,408,500	269,361,100
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	1,301,400	993,300
Weighted Average Number of Shares Outstanding, Diluted	260,709,900	270,354,400
Net Income Per Common Share
Basic	$ 0.88	$ 0.79
Assuming Dilution	$ 0.88	$ 0.79