Quarterly report pursuant to Section 13 or 15(d)

Disposals (Details)

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Disposals (Details) - USD ($)
$ / shares in Units, $ in Millions
 3 Months Ended 6 Months Ended 12 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Deferred income tax liabilities         $ 303.0
Liberty Ventures common stock | GCI Liberty | Spinoff          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Income (Loss) from Discontinued Operations and Disposal of Discontinued Operations, Net of Tax, Per Basic Share   $ 0.11 $ 1.64 $ 4.01  
Income (Loss) from Discontinued Operations, Net of Tax, Per Diluted Share   $ 0.11 $ 1.62 $ 3.96  
Evite | GCI Liberty | Spinoff          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Revenue $ 0.0 $ 6.0 $ 3.0 $ 10.0  
Disposal Group Net Earnings (Loss) 0.0   (2.0) (2.0)  
Disposal Group Total Assets         43.0
LendingTree | GCI Liberty | Spinoff          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Disposal Group Net Earnings (Loss) $ 0.0 2.0   3.0  
Disposal Group Total Assets         115.0
Liberty Broadband          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Current assets of Liberty Broadband         84.0
Total assets of Liberty Broadband         11,932.0
Current liabilities of Liberty Broadband         11.0
Total liabilities of Liberty Broadband         1,445.0
Equity of Liberty Broadband         10,487.0
Operating income of Liberty Broadband   (7.0)   (14.0)  
Share of earnings (loss) of affiliate of Liberty Broadband   11.0   30.0  
Gain (loss) on dilution of investment in affiliate of Liberty Broadband   (7.0)   (38.0)  
Income tax (expense) benefit of Liberty Broadband   3.0   11.0  
Net earnings (loss) attributable to Liberty Broadband shareholders of Liberty Broadband   (3.0)   (17.0)  
Liberty Broadband | GCI Liberty | Spinoff          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Investment in Liberty Broadband measured at fair value         3,635.0
Deferred income tax liabilities         $ 303.0
Earnings (loss) before income taxes   15.0 187.0 541.0  
Income tax (expense) benefit   (5.0) (46.0) $ (200.0)  
Maximum | Evite | GCI Liberty | Spinoff          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Disposal Group Net Earnings (Loss)   $ (1.0)      
Maximum | LendingTree | GCI Liberty | Spinoff          
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]          
Disposal Group Net Earnings (Loss)     $ 1.0