Represents the fair value of debt and capital lease obligations, as of the balance sheet date.

No definition available.

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

- Definition

Represents the minimum amount for which the reporting entity is required enter into or obtain an interest rate hedge.

+ References

No definition available.

+ Details

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

- Definition

Represents the final amount of a derivative instrument.

+ References

No definition available.

+ Details

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

- Definition

Represents the weighted average life of a senior credit facility.

+ References

No definition available.

+ Details

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

- Definition

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13,16)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

+ Details

Name:	us-gaap_DebtAndCapitalLeaseObligations
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage points added to the reference rate to compute the variable rate on the interest rate derivative.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeBasisSpreadOnVariableRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

Name:	us-gaap_DerivativeFixedInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_LondonInterbankOfferedRateLIBORMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=alsk_SixPointTwentyFivePercentConvertibleNotesDue2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=alsk_SeniorCreditFacilitiesAndOtherLongtermObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=alsk_The2017SeniorCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 4 - Fair Value Measurements and Derivative Financial Instruments (Details Textual) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	May 01, 2018	Dec. 31, 2017	Jun. 14, 2017
Interest Rate Swap [Member]
Derivative Final Notional Amount				$ 90,000
Derivative, Fixed Interest Rate				6.49425%
Interest Rate Swap [Member] \| London Interbank Offered Rate (LIBOR) [Member]
Derivative, Basis Spread on Variable Rate				5.00%
6.25% Convertible Notes Due 2018 [Member]
Debt Instrument, Interest Rate, Stated Percentage	6.25%	6.25%	6.25%
Debt and Capital Lease Obligations, Total			$ 10,026
6.25% Convertible Notes Due 2018 [Member] \| Fair Value, Inputs, Level 2 [Member]
Debt and Capital Lease Obligations, Fair Value Disclosures			10,026
Senior Credit Facilities and Other Long-Term Obligations [Member]
Debt and Capital Lease Obligations, Total	$ 174,200		$ 178,836
The 2017 Senior Credit Facility [Member]
Debt Instrument Covenants, Minimum Borrowing	$ 90,000
Weighted Average Life of Senior Credit Facility	2 years