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GOVERNMENT SUPPORT AND SPECTRUM MATTERS - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended
	Dec. 31, 2024	Sep. 30, 2025	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Jul. 31, 2022
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Government capital programs - Amounts received			$ 61,145	$ 72,531
Grant funds awarded during the period			16,097
Amounts accrued for reimbursable capital expenditures from government capital programs			13,634	$ 32,467
Alaska Connect Fund | Grant receivable from January 1, 2025 through December 2028
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Grants expected to be received per year		$ 25,600	25,600
Universal Service Fund programs
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Grant funds awarded annually			2,500
Connect America Fund II
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Grant funds awarded annually			8,000
Connect America Fund Phase II Program in Alaska
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Grant funds awarded annually					$ 19,700
Enhanced Alternative Connect America Cost Model
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Amount that has been funded or will be funded		102,600	$ 102,600
Grant fund term			14 years
Enhanced Alternative Connect America Cost Model | Grant receivable through 2030
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Amount that has been funded or will be funded		9,000	$ 9,000
Enhanced Alternative Connect America Cost Model | Grant receivable in year 2038
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Amount that has been funded or will be funded		6,000	6,000
High cost support program | Communication services | International Telecom
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Government capital programs - Amounts received			$ 5,500
Rural Digital Opportunity Fund Phase I
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Grant fund term			10 years
Term to deploy voice and broadband service to covered areas			6 years
Grant funds awarded annually			$ 2,300
Transfer of annual awards			1,300
Return of grants to FCC			700
Loss on disposition of assets and transfers		1,900
Accounts payable and accrued liabilities		$ 2,700	2,700
TBCP and Reconnect
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Government capital programs - Amounts received			34,000
Grant funds awarded during the period			239,000
Spent construction obligations			31,900
Replace and Remove Program
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Cost reimbursement amount funded	$ 517,000
Amounts accrued for reimbursable capital expenditures from government capital programs			$ 11,000
Reimbursement period			12 months
Replace and Remove Program | Maximum
GOVERNMENT SUPPORT AND SPECTRUM MATTERS
Amount of cost reimbursement allocated						$ 207,000

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