Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Numerator
Net Income	$ 392.9	$ 367.3	$ 751.2	$ 607.7
Denominator
Weighted Average Common Shares - Basic	197,180,400	201,151,700	197,641,300	201,888,800
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	956,100	1,280,000	1,182,500	1,077,700
Weighted Average Common Shares - Assuming Dilution	198,136,500	202,431,700	198,823,800	202,966,500
Net Income Per Common Share
Basic	$ 1.99	$ 1.83	$ 3.80	$ 3.01
Assuming Dilution	$ 1.98	$ 1.81	$ 3.78	$ 2.99