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, 2016	Mar. 31, 2015
Earnings Per Share [Abstract]
Net income	$ 24.9	$ 13.9
Add: Loss from discontinued operations	0.0	0.1
Income from continuing operations	$ 24.9	$ 14.0
Weighted-average shares outstanding – basic	44.0	44.7
Add: Potential effect of dilutive securities attributable to stock-based payments	0.7	0.8
Weighted-average shares outstanding – diluted	44.7	45.5
Earnings per share – Basic:
Income from continuing operations (in dollars per share)	$ 0.57	$ 0.31
Loss from discontinued operations (in dollars per share)	0.00	0.00
Net income (in dollars per share)	0.57	0.31
Earnings per share – Diluted:
Income from continuing operations (in dollars per share)	0.56	0.31
Loss from discontinued operations (in dollars per share)	0.00	0.00
Net income (in dollars per share)	$ 0.56	$ 0.31