Earnings Per Share (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Earnings Per Share [Abstract]
Net income	$ 12.9	$ 69.3
Exclude: (Income) loss from discontinued operations	(0.4)	0.1
Income from continuing operations	$ 12.5	$ 69.4
Weighted-average shares outstanding – basic	38.4	39.7
Add: Potential effect of dilutive securities attributable to stock-based payments	0.3	0.4
Weighted-average shares outstanding – diluted	38.7	40.1
Earnings per share – Basic:
Income from continuing operations (in dollars per share)	$ 0.33	$ 1.75
Loss from discontinued operations (in dollars per share)	0.01	0
Net income (in dollars per share)	0.34	1.75
Earnings per share – Diluted:
Income from continuing operations (in dollars per share)	0.32	1.73
Loss from discontinued operations (in dollars per share)	0.01	0
Net income (in dollars per share)	$ 0.33	$ 1.73