Joint Venture - Schedule of Certain Financial Information about Joint Venture Included on Company's Consolidated Balance Sheet (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures [Abstract]
Accumulated depreciation of IRU Assets, net	$ 87	$ 26

Accumulated depreciation indefeasible right of use assets.

No definition available.

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