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)
shares in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2015
USD ($)
shares
Sep. 30, 2014
USD ($)
shares
Sep. 30, 2015
USD ($)
entity
shares
Sep. 30, 2014
USD ($)
shares
Feb. 02, 2015
Dec. 31, 2014
USD ($)
Business            
Year founded     1979      
Principles of Consolidation            
Number of VIEs | entity     4      
Common Stock            
Stock repurchased during period, value     $ 44,324,000 $ 1,972,000    
Accounts Receivable and Allowance for Doubtful Receivables            
Period past due for write-off of trade accounts receivable     120 days      
Revenue Recognition            
Revenues $ 258,573,000 $ 240,725,000 $ 737,190,000 681,407,000    
Receivables 189,039,000   189,039,000     $ 212,441,000
Total High Cost Support Program [Member]            
Revenue Recognition            
Revenues 16,500,000 $ 16,500,000 50,600,000 $ 50,000,000    
Receivables 46,100,000   $ 46,100,000      
Common Stock - Class A [Member]            
Common Stock            
Stock repurchased during period, shares | shares     2,761 148    
Stock repurchased during period, value     $ 19,062,000 $ 1,972,000    
Stock Buyback Program [Member]            
Common Stock            
Authorized amount, repurchase of stock 5,000,000          
Stock repurchase program, remaining value authorized to be repurchased $ 94,300,000.0   $ 94,300,000.0      
Stock Buyback Program [Member] | Common Stock - Class A [Member]            
Common Stock            
Stock repurchased during period, shares | shares 400 100 2,800 100    
Stock repurchased during period, value $ 7,300,000 $ 1,300,000 $ 43,200,000 $ 1,300,000    
ACS Wireless [Member]            
Principles of Consolidation            
Voting interests acquired         33.33%  
Interests acquired from noncontrolling interest         66.67%