|**Acquisition (Tables)**                                                                                          | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     
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|**Business Combinations [Abstract]**                                                                              |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Preliminary Acquisition Price Allocation                                                                          | The acquisition price allocation for GCI Liberty is as follows (amounts in thousands):Cash and cash equivalents including restricted cash$147,957Receivables171,014Property and equipment1,211,392Goodwill966,044Intangible assets not subject to amortization572,500Intangible assets subject to amortization468,737Other assets83,422Deferred revenue(92,561)Debt, including capital leases(1,707,002)Other liabilities(251,692)Deferred income tax liabilities(276,683)Preferred stock(174,922)Non-controlling interest(7,000)$1,111,206                                                                                                                                                                                                                                                                                                                        
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|Cash and cash equivalents including restricted cash                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Receivables                                                                                                       |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Property and equipment                                                                                            |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Goodwill                                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Intangible assets not subject to amortization                                                                     |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Intangible assets subject to amortization                                                                         |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Other assets                                                                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Deferred revenue                                                                                                  |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Debt, including capital leases                                                                                    |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Other liabilities                                                                                                 |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Deferred income tax liabilities                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Preferred stock                                                                                                   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Non-controlling interest                                                                                          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
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|Pro Forma Revenue and Net Earnings                                                                                | The unaudited pro forma revenue, net earnings and basic and diluted net earnings per common share of GCI Liberty, prepared utilizing the historical financial statements of HoldCo, giving effect to acquisition accounting related adjustments made at the time of acquisition, as if the acquisition discussed above occurred on January 1, 2017, are as follows:Three months endedNine months endedSeptember 30, 2018amounts in thousands, except per share amountsRevenue$220,737664,287Net earnings (loss)$327,046(157,678)Net earnings (loss) attributable to GCI Liberty shareholders$327,173(157,242)Basic net earnings (loss) attributable to Series A and Series B GCI Liberty, Inc. shareholders per common share$3.04(1.46)Diluted net earnings (loss) attributable to Series A and Series B GCI Liberty, Inc. shareholders per common share$3.00(1.46)
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|Revenue                                                                                                           |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Net earnings (loss)                                                                                               |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Net earnings (loss) attributable to GCI Liberty shareholders                                                      |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Basic net earnings (loss) attributable to Series A and Series B GCI Liberty, Inc. shareholders per common share   |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    
|Diluted net earnings (loss) attributable to Series A and Series B GCI Liberty, Inc. shareholders per common share |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    

X- DefinitionTabular disclosure of pro forma results of operations for a material business acquisition or series of individually immaterial business acquisitions that are material in the aggregate.
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