Represents the amount of additional assets contributed to a joint venture during the period.

No definition available.

Name:	alsk_AdditionalAssetsContributedToJointVenture
Namespace Prefix:	alsk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of assets contributed to a joint venture during the period.

+ References

No definition available.

+ Details

Name:	alsk_AssetsContributedToJointVenture
Namespace Prefix:	alsk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the amount of percentage access of initial in-field lit capacity provided to the reporting entity under a joint venture operating agreement.

+ References

No definition available.

+ Details

Name:	alsk_JointVentureOperatingAgreementPercentageAccessOfInitialInFieldLitCapacity
Namespace Prefix:	alsk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the term of a sale leaseback transaction.

+ References

No definition available.

+ Details

Name:	alsk_SaleLeasebackTransactionTermOfContract
Namespace Prefix:	alsk_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the amount of the sale price of an asset sale.

+ References

No definition available.

+ Details

Name:	alsk_SalePriceOfAssetSale
Namespace Prefix:	alsk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash outflow associated with the investment in or advances to an entity in which the reporting entity shares control of the entity with another party or group.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireInterestInJointVenture
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireProductiveAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash inflow from the sale of property, plant and equipment (capital expenditures), software, and other intangible assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromSaleOfProductiveAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of acquisition of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentAdditions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash inflow before closing and debt issuance costs received by a seller-lessee in a sale-leaseback recognized in investing activities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51843-112757

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 50
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51831-112757

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 51
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51840-112757

+ Details

Name:	us-gaap_SaleLeasebackTransactionGrossProceedsInvestingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The gain (loss) recognized on initial consolidation of a variable interest entity (VIE) when the VIE is not a business (as defined).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=77990344&loc=d3e5710-111685

+ Details

Name:	us-gaap_VariableInterestEntityInitialConsolidationGainOrLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 5A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=77990344&loc=SL6759159-111685

+ Details

Name:	us-gaap_VariableInterestEntityOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	dei_LegalEntityAxis=alsk_QuintillionHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=alsk_ACSCableSystemsLLCAndQuintillionHoldingsLLCJointVentureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=alsk_IRUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ConsolidatedEntitiesAxis=alsk_ACSMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=alsk_QuintillionHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=alsk_FiberOpticNetworkMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 2 - Joint Venture (Details Textual) - USD ($) $ in Thousands				3 Months Ended				9 Months Ended
	Apr. 07, 2016	Mar. 31, 2016	Apr. 02, 2015	Sep. 30, 2017	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Sep. 30, 2017
Additional Assets Contributed to Joint Venture				$ 75	$ 75
Joint Venture Operating Agreement, Percentage Access of Initial In-field Lit Capacity						50.00%
Variable Interest Entity, Initial Consolidation, Gain (Loss)			$ 0
Quintillion Holdings, LLC [Member]
Additional Assets Contributed to Joint Venture					$ 75
ACS Cable Systems LLC and Quintillion Holdings, LLC Joint Venture [Member]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage								50.00%
ACS Cable Systems LLC and Quintillion Holdings, LLC Joint Venture [Member] \| Quintillion Holdings, LLC [Member]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage								50.00%
IRU [Member]
Assets Contributed to Joint Venture			1,844
IRU [Member] \| Quintillion Holdings, LLC [Member]
Assets Contributed to Joint Venture			922
Payments to Acquire Interest in Joint Venture			250
IRU [Member] \| ACS [Member]
Assets Contributed to Joint Venture			922
Payments to Acquire Interest in Joint Venture			250
Additional Assets Contributed to Joint Venture			$ 461
Quintillion Holdings, LLC [Member]
Sale Leaseback Transaction, Term of Contract							30 years
Sale Price of Asset Sale							$ 5,300
Proceeds from Sale of Productive Assets		$ 2,650
Fiber Optic Network [Member]
Property, Plant and Equipment, Additions							$ 11,000
Payments to Acquire Productive Assets	$ 5,500
Sale Leaseback Transaction, Term of Contract							30 years
Sale Leaseback Transaction, Gross Proceeds, Investing Activities							$ 400