Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator
Net Income	$ 1,283.8	$ 1,407.2	$ 981.0
Denominator
Weighted Average Common Shares - Basic	196,659,700	200,647,200	204,232,900
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	942,300	1,462,200	615,000.0
Weighted Average Common Shares - Assuming Dilution	197,602,000	202,109,400	204,847,900
Net Income Per Common Share
Basic	$ 6.53	$ 7.01	$ 4.80
Assuming Dilution	$ 6.50	$ 6.96	$ 4.79