Income from Continuing Operations Per Unrestricted Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations	$ 36.6	$ 4.1	$ 36.2	$ 1.9
Dilutive Effect on Income of Equity-based Compensation Equivalent Shares	0.0	0.0	0.0	0.0
Diluted Income from Continuing Operations Attributed to Unrestricted Shares	$ 36.3	$ 4.1	$ 36.0	$ 2.1
Weighted-Average Unrestricted Shares Outstanding (shares)	51,286,200	51,107,700	51,279,600	51,149,600
Equity-based Compensation Equivalent Shares (shares)	124,900	11,300	157,600	9,600
Weighted-Average Unrestricted Shares and Equivalent Shares Outstanding Assuming Dilution (shares)	51,411,100	51,119,000	51,437,200	51,159,200
Basic Income from Continuing Operations Per Unrestricted Share	$ 0.71	$ 0.08	$ 0.70	$ 0.04
Diluted Income from Continuing Operations Per Unrestricted Share	$ 0.71	$ 0.08	$ 0.70	$ 0.04
Unrestricted Shares [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations	$ 36.3	$ 4.1	$ 36.0	$ 2.1
Participating Awards [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations	$ 0.3	$ 0.0	$ 0.2	$ (0.2)