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Property, Plant And Equipment (Narrative) (Details) - USD ($)
$ in Millions
1 Months Ended 12 Months Ended
Jan. 31, 2019
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Property, Plant and Equipment [Line Items]        
Fixed assets were reclassified to assets held for sale   $ 1,049    
Capital Leased Assets, Gross   167 $ 152 $ 171
Proceeds from sale of property     $ 106 $ 106
Towers [Member]        
Property, Plant and Equipment [Line Items]        
Proceeds from sale of property $ 76      
Gain on sale of property 75      
Aggregate carrying value of the towers $ 1      
Accounting Standards Update 2016-02 [Member]        
Property, Plant and Equipment [Line Items]        
Cumulative-effect adjustment, Net of tax   15    
Cumulative-effect adjustment   $ 11