Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income from continuing operations	$ 37.0	$ 60.3	$ 84.2	$ 101.5
Net income from discontinued operations	2.3	7.7	1.4	8.0
Net income	$ 39.3	$ 68.0	$ 85.6	$ 109.5
Denominator:
Denominator for basic earnings per share — weighted average shares	34.9	36.0	34.9	36.2
Effect of dilutive securities:
Equity compensation plans	0.5	0.7	0.5	0.7
Weighted-average shares outstanding - diluted	35.4	36.7	35.4	36.9
Basic earnings per share from continuing operations (in dollars per share)	$ 1.06	$ 1.68	$ 2.41	$ 2.80
Basic earnings per share from discontinued operations (in dollars per share)	0.06	0.21	0.04	0.22
Basic earnings per share from consolidated operations (in dollars per share)	1.12	1.89	2.45	3.02
Diluted earnings per share from continuing operations (in dollars per share)	1.05	1.65	2.38	2.75
Diluted earnings per share from discontinued operations (in dollars per share)	0.06	0.21	0.04	0.22
Diluted earnings per share from discontinued operations (in dollars per share)	$ 1.11	$ 1.86	$ 2.42	$ 2.97