Annual report pursuant to Section 13 and 15(d)

Assets and Liabilities Measured at Fair Value (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details)

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Assets and Liabilities Measured at Fair Value (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($)
$ in Millions
 1 Months Ended 12 Months Ended
Jun. 30, 2018
Dec. 31, 2018
Mar. 09, 2018
Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash equivalents   $ 310   $ 655
Equity Securities       2,275
Indemnification asset   79 $ 281  
Debt   1,334   1,846
Indemnification payment from GCI Liberty, Inc.   133    
Fair Value, Inputs, Level 1        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Cash equivalents   310   655
Equity Securities       2,275
Significant Other Observable Inputs (Level 2)        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Indemnification asset   79    
Debt   $ 1,334   $ 1,846
1.75% Exchangeable Senior Debentures due 2046        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Interest rate (as a percent)   1.75%    
Securities repurchased 417,759      
Debt Instrument, Repurchase Amount $ 457      
Exchangeable debenture securities outstanding   332,241    
1.75% Exchangeable Senior Debentures due 2046 | GCI Liberty        
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]        
Indemnification payment from GCI Liberty, Inc. $ 133