Income from Continuing Operations Per Unrestricted Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations	$ 68.6	$ 55.6	$ 159.7	$ 93.5
Dilutive Effect on Income of Equity-based Compensation Equivalent Shares	0	0	0	0
Diluted Income from Continuning Operations Attributed to Unrestricted Shares	68.3	55.3	158.9	93.0
Weighted-Average Unrestricted Shares Outstanding	56,365,800	58,299,700	57,374,400	59,155,500
Equity-based Compensation Equivalent Shares	135,700	171,900	118,800	146,600
Weighted-Average Unrestricted Shares and Equivalent Shares Outstanding Assuming Dilution	56,501,500	58,471,600	57,493,200	59,302,100
Basic Income from Continuing Operations Per Unrestricted Share (in dollars per share)	$ 1.21	$ 0.95	$ 2.77	$ 1.57
Diluted Income from Continuing Operations Per Untrestriced Share (in dollars per share)	$ 1.21	$ 0.95	$ 2.76	$ 1.56
Restricted Shares [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations	0.3	0.3	0.8	0.5
Unrestricted Shares [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations	$ 68.3	$ 55.3	$ 158.9	$ 93.0