Income From Continuing Operations Per Unrestricted Share (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations	$ 1.3	$ 38.0	$ 27.4	$ 13.5	$ 63.3	$ 4.8	$ 9.3	$ 35.2	$ 80.2	$ 112.6	$ 214.5
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									$ 79.8	$ 112.1	$ 213.4
Weighted-Average Unrestricted Shares Outstanding (in shares)									51,606,900	53,762,500	56,856,900
Equity-based Compensation Equivalent Shares (in shares)									76,600	105,400	126,700
Weighted-average Unrestricted Shares and Equivalent Shares Outstanding Assuming Dilution ( in shares)									51,683,500	53,867,900	56,983,600
Basic Income from Continuing Operations Per Unrestricted Share (per share)	$ 0.03	$ 0.73	$ 0.53	$ 0.26	$ 1.20	$ 0.09	$ 0.17	$ 0.63	$ 1.55	$ 2.08	$ 3.75
Diluted Income from Continuing Operations Per Unrestricted Share (per share)	$ 0.03	$ 0.73	$ 0.53	$ 0.26	$ 1.20	$ 0.09	$ 0.17	$ 0.63	$ 1.55	$ 2.08	$ 3.74
Common Stock [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations									$ 79.8	$ 112.1	$ 213.4
Participating Awards [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations									$ 0.4	$ 0.5	$ 1.1