Income Per Common Share Computations (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	$ 14.1	$ 2.2
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	14.1	2.2
Distributed Earnings	0.0	0.1
Income (Loss) from Discontinued Operations, Net of Tax, Attributable to Parent	167.9	5.1
Net Income (Loss) Available to Common Stockholders, Basic	182.0	7.2
Net Income (Loss) from Continuing Operations Available to Common Shareholders, Diluted	14.1	2.2
Net Income (Loss) Available to Common Stockholders, Diluted	$ 182.0	$ 7.3
Earnings Per Share, Basic and Diluted [Abstract]
Numerator for diluted net income per common share:	14.4	16.3
Plus dilutive effect of stock awards	0.1	0.2
Denominator for net income per common share:	0.0	0.3
Basic	14.5	16.8
Earnings Per Share, Diluted [Abstract]
Diluted	$ 12.61	$ 0.44
Diluted	12.55	0.44
Income (Loss) from Continuing Operations, Per Basic Share	0.98	0.13
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share	11.63	0.31
Income (Loss) from Continuing Operations, Per Diluted Share	0.97	0.13
Discontinued Operation, Income (Loss) from Discontinued Operation, Net of Tax, Per Diluted Share	$ 11.58	$ 0.31