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Description Of Business And Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Property, Plant and Equipment [Line Items]      
Ownership percentage 50.00%    
Cash equivalent, maturity period three months or less    
Cash invested in money market funds, outstanding balances $ 42.5 $ 114.6  
Reserve for uncollectible accounts 7.7 3.9  
Minimum percentage of revenue accounted for by one customer 10.00% 10.00% 10.00%
State tax net operating losses, valuation allowance $ 0.1    
Percentage of likelihood of impairment more than 50 percent    
Building And Improvements [Member]
      
Property, Plant and Equipment [Line Items]      
Property and equipment estimated life, minimum, years 1    
Property and equipment estimated life, maximum, years 8    
Computer Equipment And Software [Member]
      
Property, Plant and Equipment [Line Items]      
Property and equipment estimated life, minimum, years 1    
Property and equipment estimated life, maximum, years 5    
Furniture And Equipment [Member]
      
Property, Plant and Equipment [Line Items]      
Property and equipment estimated life, minimum, years 1    
Property and equipment estimated life, maximum, years 10    
Transportation Equipment And Automobiles [Member]
      
Property, Plant and Equipment [Line Items]      
Property and equipment estimated life, minimum, years 1    
Property and equipment estimated life, maximum, years 10    
Developed Software Projects [Member]
      
Property, Plant and Equipment [Line Items]      
Maximum useful life, years 5