Acquisitions And Divestitures Acquisition of Unwired Holdings, Inc. (Details) (USD $)
In Millions, unless otherwise specified
 1 Months Ended 3 Months Ended
Oct. 31, 2014
Mar. 31, 2015
Dec. 31, 2014
Oct. 01, 2014
Business Acquisition [Line Items]        
Goodwill   611 $ 656  
Unwired Holdings, Inc.        
Business Acquisition [Line Items]        
Business Acquisition, Percentage of Equity Interests Acquired       100.00%
Purchase price, cash consideration 190      
Acquired cash, excess net working capital and certain tax benefits from acquisition 19      
Total purchase price 209      
Definite-lived intangible assets       63
Other assets purchased and liabilities assumed, net       19
Identifiable net assets acquired       82
Goodwill       127
Total purchase price allocation       $ 209
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life   10 years