Net Income Per Common Share (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Numerator
Net Income	$ 242.5	$ 218.6	$ 471.4	$ 431.2
Denominator (000s)
Weighted Average Number of Shares Outstanding, Basic	256,790,200	265,560,400	258,092,700	267,452,000
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	1,119,500	1,175,900	1,210,400	1,084,600
Weighted Average Number of Shares Outstanding, Diluted	257,909,700	266,736,300	259,303,100	268,536,600
Net Income Per Common Share
Basic	$ 0.94	$ 0.82	$ 1.83	$ 1.61
Assuming Dilution	$ 0.94	$ 0.82	$ 1.82	$ 1.61