Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Basic earnings per share:
Income from continuing operations	$ 34.0	$ 33.5	$ 53.7	$ 35.1
Weighted average number of shares outstanding (in shares)	31.9	31.9	31.9	31.9
Basic earnings per share from continuing operations (in dollars per share)	$ 1.07	$ 1.05	$ 1.69	$ 1.10
Diluted earnings per share:
Income from continuing operations	$ 34.0	$ 33.5	$ 53.7	$ 35.1
Weighted average number of shares outstanding (in shares)	31.9	31.9	31.9	31.9
Effect of dilutive securities:
Restricted stock (in shares)	0.1	0.2	0.1	0.4
Total shares and dilutive securities (in shares)	32.0	32.1	32.0	32.3
Diluted earnings per share from continuing operations (in dollars per share)	$ 1.06	$ 1.04	$ 1.68	$ 1.09