| Cover | Nov. 17, 2020 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Nov. 17, 2020 |
| Entity File Number | 001-38385 |
| Entity Registrant Name | GCI LIBERTY, INC. |
| Entity Central Index Key | 0000808461 |
| Entity Tax Identification Number | 92-0072737 |
| Entity Incorporation, State or Country Code | DE |
| 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 | 875-5900 |
| Written Communications | false |
| Soliciting Material | true |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
| Series Common Stock Par Value 0.01 Per Share [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Series A Common Stock, par value $0.01 per share |
| Trading Symbol | GLIBA |
| Security Exchange Name | NASDAQ |
| Series Cumulative Redeemable Preferred Stock Par Value 0.01 Per Share [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Series A Cumulative Redeemable preferred stock, par value $0.01 per share |
| Trading Symbol | GLIBP |
| Security Exchange Name | NASDAQ |
