Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.0.8
Business and Summary of Significant Accounting Principles (Narratives) (Details) (USD $)
 3 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Dec. 31, 2012
Business and Summary of Significant Accounting Policies [Abstract]          
Year Founded     1979    
Statement [Line Items]          
Revenues $ 189,661,000 $ 176,104,000 $ 375,877,000 $ 348,011,000  
Receivables 167,465,000   167,465,000   150,436,000
Class of Stock [Line Items]          
Stock Repurchase Program, Remaining Value Authorized to be Repurchased     98,400,000    
Common Stock - Class A [Member] | Stock Buyback Program [Member] | Number of shares repurchased [Member]
          
Class of Stock [Line Items]          
Stock Repurchased During Period, Shares 735,000 6,000 1,500,000 869,000  
Common Stock - Class A [Member] | Stock Buyback Program [Member] | Value of shares repurchased [Member]
          
Class of Stock [Line Items]          
Stock Repurchased During Period, Value 6,300,000 100,000 12,900,000 9,000,000  
Total High Cost Support Program [Member]
          
Statement [Line Items]          
Revenues 10,500,000 10,000,000 21,100,000 21,100,000  
Receivables $ 33,700,000   $ 33,700,000