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 6 Months Ended
Jun. 30, 2015
USD ($)
shares
Jun. 30, 2014
USD ($)
Jun. 30, 2015
USD ($)
entity
shares
Jun. 30, 2014
USD ($)
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     $ 36,939,000 $ 536,000    
Accounts Receivable and Allowance for Doubtful Receivables            
Period past due for write-off of trade accounts receivable     120 days      
Revenue Recognition            
Revenues $ 247,528,000 $ 224,399,000 $ 478,617,000 440,682,000    
Receivables 182,337,000   182,337,000     $ 212,441,000
Total High Cost Support Program [Member]            
Revenue Recognition            
Revenues 16,900,000 $ 17,000,000 34,100,000 $ 33,500,000    
Receivables 45,300,000   $ 45,300,000      
Common Stock - Class A [Member]            
Common Stock            
Stock repurchased during period, shares | shares     2,331 29    
Stock repurchased during period, value     $ 18,808,000 $ 536,000    
Stock Buyback Program [Member]            
Common Stock            
Authorized amount, repurchase of stock 5,000,000.0   5,000,000.0      
Stock repurchase program, remaining value authorized to be repurchased $ 96,600,000.0   $ 96,600,000.0      
Stock Buyback Program [Member] | Common Stock - Class A [Member]            
Common Stock            
Stock repurchased during period, shares | shares 1,200   2,300 0    
Stock repurchased during period, value $ 19,700,000   $ 35,900,000      
ACS Wireless [Member]            
Principles of Consolidation            
Voting interests acquired         33.33%  
Interests acquired from noncontrolling interest         66.67%