| Document and Entity Information | Feb. 26, 2021 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Period End Date | Feb. 26, 2021 |
| Entity Registrant Name | LIBERTY BROADBAND CORPORATION |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-36713 |
| Entity Tax Identification Number | 47-1211994 |
| Entity Address, Address Line One | 12300 Liberty Blvd. |
| Entity Address, City or Town | Englewood |
| Entity Address, State or Province | CO |
| Entity Address, Postal Zip Code | 80112 |
| City Area Code | 720 |
| Local Phone Number | 875-5700 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001611983 |
| Amendment Flag | false |
| Common Class A | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Series A common stock |
| Trading Symbol | LBRDA |
| Security Exchange Name | NASDAQ |
| Common Class C | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Series C common stock |
| Trading Symbol | LBRDK |
| Security Exchange Name | NASDAQ |
| Preferred Class A | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Series A Cumulative Redeemable preferred stock |
| Trading Symbol | LBRDP |
| Security Exchange Name | NASDAQ |
