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Common Stock (Employee Stock Purchase Plan) (Details) (USD $)
In Millions, except Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2013
Employee Stock [Member]
Dec. 31, 2012
Employee Stock [Member]
May 18, 2012
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]            
Registered shares of common stock           500,000
Percent of common stock fair market value       85.00%    
Offering period       3 months    
Maximum employee compensation payroll deductions may not exceed       10.00%    
Maximum shares employees may purchase in any one offering period       1,000    
Share based compensation expense $ 10.9 $ 13.4 $ 7.4 $ 0.1 $ 0.1  
Total fair value of the shares purchased under the plan       $ 0.9 $ 0.2