Note 9 - Accumulated Other Comprehensive Loss (Details Textual) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Estimated Reclassification from Accumulated Other Comprehensive Income Within Next Twelve Months	$ 686

The amount of reclassification from accumulated other comprehensive income estimated to occur within the next twelve months.

No definition available.

Name:	alsk_EstimatedReclassificationFromAccumulatedOtherComprehensiveIncomeWithinNextTwelveMonths
Namespace Prefix:	alsk_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration