Represents the annual cap of rural health care universal service support mechanism.

No definition available.

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

- Definition

Represents the percentage of refund available under the rural health care universal support mechanism.

+ References

No definition available.

+ Details

Name:	alsk_PercentageOfRefundAvailable
Namespace Prefix:	alsk_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount due from customers or clients, within one year of the balance sheet date (or the normal operating cycle, whichever is longer), for goods or services (including trade receivables) that have been delivered or sold in the normal course of business, reduced to the estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(4))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_AccountsReceivableNetCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The increase (decrease) during the reporting period in amount due within one year (or one business cycle) from customers for the credit sale of goods and services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

+ Details

Name:	us-gaap_IncreaseDecreaseInAccountsReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_MajorCustomersAxis=alsk_RuralHealthCareCustomersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 4 - Accounts Receivable (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Apr. 10, 2017	Dec. 31, 2016
Annual Cap of Rural Health Care Support			$ 400,000
Percentage of Refund Available			92.50%
Increase (Decrease) in Accounts Receivable	$ 1,102
Accounts Receivable, Net, Current		$ 32,535		$ 25,062
Rural Health Care Customers [Member]
Accounts Receivable, Net, Current		$ 8,580