v3.10.0.1
Document and Entity Information - USD ($)
$ in Billions
12 Months Ended
Dec. 31, 2018
Jan. 31, 2019
Jun. 29, 2018
Entity Registrant Name Liberty Broadband Corp    
Entity Central Index Key 0001611983    
Document Type 10-K    
Document Period End Date Dec. 31, 2018    
Amendment Flag false    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 13.0
Entity Small Business false    
Entity Emerging Growth Company false    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Series A common stock      
Entity Common Stock, Shares Outstanding   26,313,600  
Series B common stock      
Entity Common Stock, Shares Outstanding   2,454,520  
Series C common stock      
Entity Common Stock, Shares Outstanding   152,591,984