Income From Continuing Operations Per Unrestricted Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income (Loss) from Continuing Operations	$ 29.1	$ (18.3)	$ 4.1	$ (2.2)	$ 1.3	$ 38.0	$ 27.4	$ 13.5	$ 12.7	$ 80.2	$ 112.6
Dilutive Effect on Income of Equity-based Compensation Equivalent Shares									0.0	0.0	0.0
Diluted Income from Continuing Operations Attributed to Unrestricted Shares									$ 12.9	$ 79.8	$ 112.1
Weighted-Average Unrestricted Shares Outstanding (in shares)									51,156,100	51,606,900	53,762,500
Equity-based Compensation Equivalent Shares (in shares)									58,600	76,600	105,400
Weighted-average Unrestricted Shares and Equivalent Shares Outstanding Assuming Dilution ( in shares)									51,214,700	51,683,500	53,867,900
Basic Income from Continuing Operations Per Unrestricted Share (per share)	$ 0.56	$ (0.36)	$ 0.08	$ (0.04)	$ 0.03	$ 0.73	$ 0.53	$ 0.26	$ 0.25	$ 1.55	$ 2.08
Diluted Income from Continuing Operations Per Unrestricted Share (per share)	$ 0.56	$ (0.36)	$ 0.08	$ (0.04)	$ 0.03	$ 0.73	$ 0.53	$ 0.26	$ 0.25	$ 1.55	$ 2.08
Common Stock [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income (Loss) from Continuing Operations									$ 12.9	$ 79.8	$ 112.1
Participating Awards [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income (Loss) from Continuing Operations									$ (0.2)	$ 0.4	$ 0.5