Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator
Net Income	$ 410.7	$ 328.6	$ 1,034.6	$ 664.5
Denominator
Weighted Average Common Shares - Basic	200,035,300	204,645,800	201,262,300	204,429,600
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	1,614,900	496,500	1,256,700	623,300
Weighted Average Common Shares - Assuming Dilution	201,650,200	205,142,300	202,519,000	205,052,900
Net Income Per Common Share
Basic	$ 2.05	$ 1.61	$ 5.14	$ 3.25
Assuming Dilution	$ 2.04	$ 1.60	$ 5.11	$ 3.24