v3.10.0.1
Document and Entity Information - shares
9 Months Ended
Sep. 30, 2018
Oct. 15, 2018
Entity Registrant Name Liberty Broadband Corp  
Entity Central Index Key 0001611983  
Document Type 10-Q  
Document Period End Date Sep. 30, 2018  
Amendment Flag false  
Current Fiscal Year End Date --12-31  
Entity Current Reporting Status Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q3  
Series A common stock    
Entity Common Stock, Shares Outstanding   26,309,573
Series B common stock    
Entity Common Stock, Shares Outstanding   2,454,943
Series C common stock    
Entity Common Stock, Shares Outstanding   152,588,667