| Document and Entity Information | Mar. 12, 2021 |
| Cover [Abstract] | |
| Entity Registrant Name | ALASKA COMMUNICATIONS SYSTEMS GROUP INC |
| Amendment Flag | false |
| Entity Central Index Key | 0001089511 |
| Document Type | 8-K |
| Document Period End Date | Mar. 12, 2021 |
| Entity Incorporation State 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 | false |
| Pre Commencement Tender Offer | false |
| Pre Commencement Issuer Tender Offer | false |
| Security 12b Title | Common stock, $.01 par value per share |
| Trading Symbol | ALSK |
| Security Exchange Name | NASDAQ |
| Entity Emerging Growth Company | false |
