| Document And Entity Information | Dec. 15, 2020 |
| Document Information [Line Items] | |
| Entity, Registrant Name | ALASKA COMMUNICATIONS SYSTEMS GROUP, INC. |
| Document, Type | 8-K |
| Document, Period End Date | Dec. 15, 2020 |
| Entity, Incorporation, State or Country Code | DE |
| Entity, File Number | 001-38341 |
| Entity, Tax Identification Number | 52-2126573 |
| Entity, Address, Address Line One | 600 Telephone Avenue |
| Entity, Address, City or Town | Anchorage |
| Entity, Address, State or Province | AK |
| Entity, Address, Postal Zip Code | 99503-6091 |
| City Area Code | 907 |
| Local Phone Number | 297 – 3000 |
| Written Communications | false |
| Soliciting Material | true |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common stock |
| Trading Symbol | ALSK |
| Security Exchange Name | NASDAQ |
| Entity, Emerging Growth Company | false |
| Amendment Flag | false |
| Entity, Central Index Key | 0001089511 |
