Earnings Per Share (Schedule of Earnings Per Share Basic and Diluted) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share [Abstract]
Net Income (Loss) Attributable to Parent									$ 902.0	$ 517.0	$ 1,170.0
Weighted Average Number of Shares Outstanding, Diluted [Abstract]
Weighted Average Number of Shares Outstanding, Basic									66,300	66,900	67,800
Equivalent shares from outstanding stock options									800	800	500
Weighted Average Number of Shares Outstanding, Diluted									67,100	67,700	68,300
Basic earnings per share:
Basic earnings per share	$ 2.40	$ 4.34	$ 3.09	$ 3.77	$ 4.36	$ (1.13)	$ 1.57	$ 2.93	$ 13.60	$ 7.73	$ 17.26
Diluted earnings per share	$ 2.37	$ 4.29	$ 3.05	$ 3.72	$ 4.30	$ (1.13)	$ 1.55	$ 2.91	$ 13.44	$ 7.64	$ 17.13
Net Income	$ 160.0	$ 289.0	$ 207.0	$ 253.0	$ 293.0	$ (75.0)	$ 106.0	$ 197.0	$ 909.0	$ 521.0	$ 1,170.0
Net income attributable to noncontrolling interest									$ 7.0	$ 4.0	$ 0.0