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 3 Months Ended 3 Months Ended
Mar. 31, 2014
entity
Mar. 31, 2013
Dec. 31, 2013
Mar. 31, 2014
Total High Cost Support Program [Member]
Mar. 31, 2013
Total High Cost Support Program [Member]
Mar. 31, 2014
Common Stock - Class A [Member]
Mar. 31, 2013
Common Stock - Class A [Member]
Jul. 22, 2013
ACS [Member]
Mar. 31, 2014
Stock Buyback Program [Member]
Mar. 31, 2013
Stock Buyback Program [Member]
Common Stock - Class A [Member]
Business                    
Year founded 1979                  
Principles of Consolidation                    
Number of VIEs 4                  
Acquisition                    
Percentage of voting interests acquired               33.33%    
Earnings Per Share                    
Shares contingently issuable 0 58,000                
Common Stock                    
Authorized amount, repurchase of stock $ 5,000,000.0                  
Stock repurchased during period, shares           26,000 795,000     764,000
Stock repurchased during period, value 529,000 6,714,000       529,000 6,804,000     6,600,000
Stock repurchase program, remaining value authorized to be repurchased                 111,100,000  
Accounts Receivable and Allowance for Doubtful Receivables                    
Period past due for write-off of trade accounts receivable 120 days                  
Revenue Recognition                    
Revenues 216,283,000 186,216,000   16,500,000 10,600,000          
Receivables $ 219,050,000   $ 228,372,000 $ 46,400,000