Additional assets contributed to joint venture.

No definition available.

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

- Definition

Assets contributed to joint venture.

+ References

No definition available.

+ Details

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

- Definition

Reduction in carrying value of fiber and indefeasible right of use assets.

+ References

No definition available.

+ Details

Name:	alsk_ReductionInCarryingValueOfFiberAndIndefeasibleRightOfUseAssets
Namespace Prefix:	alsk_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Sale leaseback transaction term of contract.

+ References

No definition available.

+ Details

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

- Definition

Sale price of asset sale.

+ References

No definition available.

+ Details

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

- Definition

Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

+ Details

Name:	invest_InvestmentLineItems
Namespace Prefix:	invest_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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=66902209&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
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: 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=66902209&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=66902209&loc=d3e3179-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

+ 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=28365400&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=28365400&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=28365400&loc=d3e51840-112757

+ Details

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

- Definition

A description of the terms of the lease(s) related to the assets being leased-back in connection with the transaction involving the sale of property to another party and the lease of the property back to the seller.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6456341&loc=d3e50796-112755

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6452660&loc=d3e36991-112694

+ Details

Name:	us-gaap_SaleLeasebackTransactionLeaseTerms
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
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=64801991&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=64801991&loc=SL6759159-111685

+ Details

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

- Details

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

- Details

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

- Details

Name:	dei_LegalEntityAxis=us-gaap_ParentCompanyMember
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:

- Details

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

Joint Venture - Additional Information (Detail) - USD ($)				3 Months Ended	6 Months Ended	9 Months Ended
	Apr. 07, 2016	Mar. 31, 2016	Apr. 02, 2015	Sep. 30, 2016	Sep. 30, 2016	Sep. 30, 2016
Investment [Line Items]
Additional Contribution to Joint Venture				$ 75,000		$ 461,000
Voting interest in joint venture						50.00%
Gain or loss recorded on initial consolidation of Joint Venture					$ 0
Reduction in carrying value of fiber and IRUs				461,000	461,000	$ 461,000
IRU [Member]
Investment [Line Items]
Contribution to Joint Venture			$ 1,844,000
Cash Contribution to Joint Venture			250,000
Quintillion Holdings, LLC [Member]
Investment [Line Items]
Term of indefeasible right of use						30 years
Sale price of fiber strands				5,300,000	$ 5,300,000	$ 5,300,000
Payment received in connection with sale of 46 fiber strands from the Fiber Optic System at closing date		$ 2,650,000
Additional Contribution to Joint Venture				$ 75,000
Quintillion Holdings, LLC [Member] \| IRU [Member]
Investment [Line Items]
Contribution to Joint Venture			922,000
Cash Contribution to Joint Venture			250,000
ACS [Member] \| IRU [Member]
Investment [Line Items]
Contribution to Joint Venture			922,000
Additional Contribution to Joint Venture			$ 461,000
Fiber Optic Network [Member]
Investment [Line Items]
Purchase price of fiber strand optic cable						$ 11,000,000
Purchase price paid at closing	$ 5,500,000
Term of fibers indefeasible right of use sold to CPAI						The Company, through its wholly-owned subsidiary ACS Cable Systems, LLC, acquired a fiber optic cable system (including conduit, licenses, permits and right-of-ways) running from the Kuparuk Operating Center to the Trans-Alaska Pipeline System Pump Station #1 (the "Fiber Optic System").
Term of indefeasible right of use						30 years
Sale price of indefeasible right of use of fibers to CPAI						$ 400,000
ACS Cable Systems LLC and Quintillion Holdings, LLC Joint Venture [Member]
Investment [Line Items]
Voting interest in joint venture			50.00%			50.00%
ACS Cable Systems LLC and Quintillion Holdings, LLC Joint Venture [Member] \| Quintillion Holdings, LLC [Member]
Investment [Line Items]
Voting interest in joint venture			50.00%