Basic and Diluted Earnings Per Share (Detail) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($) $ / shares shares	Mar. 31, 2022 USD ($) $ / shares shares	Mar. 31, 2022 $ / shares
Numerator
Net Income | $	$ 358.3	$ 240.4
Denominator
Weighted Average Common Shares - Basic	198,111,200	202,628,800
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	1,408,900	875,500
Weighted Average Common Shares - Assuming Dilution	199,520,100	203,504,300
Net Income Per Common Share
Basic | (per share)	$ 1.81	$ 1.19	$ 1.19
Assuming Dilution | (per share)	$ 1.80	$ 1.18	$ 1.18