Document And Entity Information - USD ($)	Dec. 31, 2020	Apr. 16, 2021	Jun. 30, 2020
Document Information [Line Items]
Entity, Registrant Name	Alaska Communications Systems Group, Inc.
Current Fiscal Year End Date	--12-31
Document, Fiscal Period Focus	FY
Document, Fiscal Year Focus	2020
Document, Type	10-K/A
Document, Annual Report	true
Document, Period End Date	Dec. 31, 2020
Document, Transition Report	false
Entity, File Number	001-38341
Entity, Incorporation, State or Country Code	DE
Entity, Tax Identification Number	52-2126573
Entity, Address, Address Line One	600 Telephone Avenue
Entity, Address, Postal Zip Code	99503-6091
Entity, Address, City or Town	Anchorage
Entity, Address, State or Province	AK
City Area Code	907
Local Phone Number	297-3000
Title of 12(b) Security	Common Stock
Trading Symbol	ALSK
Security Exchange Name	NASDAQ
Entity, Well-known Seasoned Issuer	No
Entity, Voluntary Filers	No
Entity, Current Reporting Status	Yes
Entity, Interactive Data, Current	Yes
Entity, Filer Category	Accelerated Filer
Entity, Small Business	true
Entity, Emerging Growth Company	false
Entity, Shell Company	false
Entity, Public Float			$ 147,000,000
Entity, Common Stock Shares, Outstanding		54,273,804
Amendment Description	Alaska Communications Systems Group, Inc. and its consolidated subsidiaries (“we,” “our,” “us,” the “Company” and “Alaska Communications”) is filing this Amendment No. 1 on Form 10-K/A for the year ended December 31, 2020 (“Amendment”) to amend our Form 10-K for the year ended December 31, 2020, filed with the Securities and Exchange Commission (the “SEC”) on March 16, 2021 (the “Original Form 10-K”). We are filing this Amendment to (i) present in Part I, Item 1A, a revised risk factor, as described in Item 503(c) of Regulation S-K, that is applicable to the Company [required if there are changes from the original 10-K]; and (ii) present the information required by Part III of Form 10-K that was previously omitted from the Original Form 10-K in reliance on General Instruction G(3) to Form 10-K. The Company is hereby amending the Original Form 10-K as follows:
Amendment Flag	true
Entity, Central Index Key	0001089511

ALASKA COMMUNICATIONS SYSTEMS GROUP INC 10-K/A