Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Numerator
Net Income	$ 738.5	$ 1,779.1	$ 1,283.8
Denominator
Weighted Average Common Shares - Basic	172,511,500	187,497,700	196,659,700
Dilution for Assumed Exercises of Stock Options and Nonvested Stock Awards	410,100	571,500	942,300
Weighted Average Common Shares - Assuming Dilution	172,921,600	188,069,200	197,602,000
Net Income Per Common Share
Basic	$ 4.28	$ 9.49	$ 6.53
Assuming Dilution	$ 4.27	$ 9.46	$ 6.50