Income (Loss) from Continuing Operations Per Unrestricted Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income (Loss) from Continuing Operations	$ 47.8	$ (18.3)	$ 84.0	$ (16.4)
Dilutive Effect on Income of Equity-based Compensation Equivalent Shares	0.0	0.0	0.0	0.0
Diluted Income (Loss) from Continuing Operations Attributed to Unrestricted Shares	$ 47.4	$ (18.2)	$ 83.4	$ (16.1)
Weighted-Average Unrestricted Shares Outstanding (shares)	51,366,800	51,122,500	51,308,700	51,140,600
Equity-based Compensation Equivalent Shares (shares)	199,600	0	171,600	0
Weighted-Average Unrestricted Shares and Equivalent Shares Outstanding Assuming Dilution (shares)	51,566,400	51,122,500	51,480,300	51,140,600
Basic Income (Loss) from Continuing Operations Per Unrestricted Share	$ 0.92	$ (0.36)	$ 1.63	$ (0.31)
Diluted Income (Loss) from Continuing Operations Per Unrestricted Share	$ 0.92	$ (0.36)	$ 1.62	$ (0.31)
Unrestricted Shares [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income (Loss) from Continuing Operations	$ 47.4	$ (18.2)	$ 83.4	$ (16.1)
Participating Awards [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income (Loss) from Continuing Operations	$ 0.4	$ (0.1)	$ 0.6	$ (0.3)