Income from Continuing Operations Per Unrestricted Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations	$ 58.6	$ 36.3
Dilutive Effect on Income of Equity-based Compensation Equivalent Shares	0	0
Diluted Income from Continuning Operations Attributed to Unrestricted Shares	58.3	36.1
Weighted-Average Unrestricted Shares Outstanding	58,130,500	59,865,700
Equity-based Compensation Equivalent Shares	110,300	130,400
Weighted-Average Unrestricted Shares and Equivalent Shares Outstanding Assuming Dilution	58,240,800	59,996,100
Basic Income from Continuing Operations Per Unrestricted Share	$ 1.00	$ 0.61
Diluted Income from Continuing Operations Per Untrestriced Share	$ 1.00	$ 0.60
Restricted Shares [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations	0.3	0.2
Unrestricted Shares [Member]
Schedule of Basic and Diluted Earnings Per Share [Line Items]
Income from Continuing Operations	$ 58.3	$ 36.1