Stock-Based Compensation Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended	9 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Jun. 30, 2011	Jun. 30, 2011	Sep. 30, 2012	Sep. 30, 2012 Deferred Compensation, Share-based Payments [Member]	Sep. 30, 2011 Deferred Compensation, Share-based Payments [Member]	Sep. 30, 2012 Deferred Compensation, Share-based Payments [Member]	Sep. 30, 2011 Deferred Compensation, Share-based Payments [Member]	Sep. 30, 2012 Stock Options SARs and Restricted Awards [Member] Years	Sep. 30, 2012 Performance Based Awards [Member] Years	Sep. 30, 2012 Contingent Compensation Data Center Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based, Compensation Cost	$ 6.4	$ 1.5	$ 5.2	$ 11.2							$ 0
Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	7.3			7.3
Deferred Compensation, Shares Outstanding					0.7	0.8
Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition									2	1
Deferred Compensation, Compensation Expense					1.4		1.9	0.3
Maximum payout of contingent compensation plan											90.0
Payout of contingent compensation plan threshold value											$ 1,000.0