Quarterly report pursuant to Section 13 or 15(d)

Business and Summary of Significant Accounting Principles (Narratives) (Details)

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Business and Summary of Significant Accounting Principles (Narratives) (Details) (USD $)
3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Dec. 31, 2012
Business and Summary of Significant Accounting Policies [Abstract]      
Year Founded 1979    
Statement [Line Items]      
Revenues $ 186,216,000 $ 171,907,000  
Receivables 163,999,000   150,436,000
Class of Stock [Line Items]      
Stock Repurchase Program, Remaining Value Authorized to be Repurchased 99,700,000    
Common Stock - Class A [Member] | Stock Buyback Program [Member] | Number of shares repurchased [Member]
     
Class of Stock [Line Items]      
Stock Repurchased During Period, Shares 764,000 862,000  
Common Stock - Class A [Member] | Stock Buyback Program [Member] | Value of shares repurchased [Member]
     
Class of Stock [Line Items]      
Stock Repurchased During Period, Value 6,600,000 9,000,000  
Total High Cost Support Program [Member]
     
Statement [Line Items]      
Revenues 10,600,000 11,100,000  
Receivables $ 34,800,000