Note 12 - Accumulated Other Comprehensive (Loss) Income (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
Estimated Reclassification from Accumulated Other Comprehensive Income Within Next Twelve Months	$ 267

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