Note 9 - Stock Incentive Plans (Details Textual)	9 Months Ended
Sep. 30, 2017 shares
Performance Share Units Granted in Period, Number for Which Performance Targets Have Not Been Established	307
Percentage of Performance Share Units Granted Based on Achievement of a Secondary Performance Condition	50.00%
Percentage of Performance Share Units Granted Based on Achievement of a Market Condition	50.00%
Performance Share Units [Member] \| Granted Prior to 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Performance Share Units [Member] \| Grants in 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	2 years 182 days

Represents the percentage of performance share units that are granted based on the achievement of a market condition.

No definition available.

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Namespace Prefix:	alsk_
Data Type:	num:percentItemType
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Period Type:	duration

- Definition

Represents the percentage of performance share units that are granted based on the achievement of a secondary performance condition.

+ References

No definition available.

+ Details

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

- Definition

Represents the number of performance share units granted during the period, for which performance targets have not been established.

+ References

No definition available.

+ Details

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Namespace Prefix:	alsk_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

+ Details

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- Details

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- Details

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Namespace Prefix:
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Period Type:

- Details

Name:	us-gaap_AwardDateAxis=alsk_GrantsIn2017Member
Namespace Prefix:
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