| Document and Entity Information | Feb. 12, 2021 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Amendment Flag | false |
| Document Period End Date | Feb. 12, 2021 |
| Entity Registrant Name | Cable One, Inc. |
| Entity Incorporation, State or Country Code | DE |
| Entity File Number | 001-36863 |
| Entity Tax Identification Number | 13-3060083 |
| Entity Address, Address Line One | 210 E. Earll Drive |
| Entity Address, City or Town | Phoenix |
| Entity Address, State or Province | AZ |
| Entity Address, Postal Zip Code | 85012 |
| City Area Code | 602 |
| Local Phone Number | 364-6000 |
| 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 | 0001632127 |
| Title of 12(b) Security | Common Stock, par value $0.01 per share |
| Trading Symbol | CABO |
| Security Exchange Name | NYSE |
