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Major Customer (Details) (Operating Revenues [Member], Sprint Nextel [Member])
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Concentration Risk [Line Items]      
Concentration risk (in hundredths) 59.00% 57.00% 60.00%
Maximum [Member]
     
Concentration Risk [Line Items]      
Concentration risk (in hundredths) 2.50% 2.50% 2.50%