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Property and equipment: (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Owned assets:
Property and equipment, gross	$ 3,642,906	$ 3,319,731
Accumulated depreciation and amortization	(1,921,832)	(1,655,564)
Property and equipment, net	1,721,074	1,664,167
Assets under finance leases:
Property and equipment, net	1,721,074	1,664,167
Depreciation and amortization expense	268,400	296,200	$ 229,900
Owned assets
Owned assets:
Property and equipment, gross	2,635,845	2,418,959
Accumulated depreciation and amortization	(1,579,825)	(1,350,672)
Property and equipment, net	1,056,020	1,068,287
IRU finance lease termination
Assets under finance leases:
IRUs	1,007,061	900,772
Less-Accumulated depreciation and amortization	(342,007)	(304,892)
IRUs, Net	665,054	595,880
Network equipment | Owned assets
Owned assets:
Property and equipment, gross	1,213,087	1,085,979
Owned buildings and leasehold improvements | Owned assets
Owned assets:
Property and equipment, gross	502,187	470,713
System infrastructure (including owned fiber) | Owned assets
Owned assets:
Property and equipment, gross	708,353	651,621
Assets under finance leases:
Capitalized compensation cost	48,400	45,900	$ 35,500
Software | Owned assets
Owned assets:
Property and equipment, gross	14,139	13,780
Office and other equipment | Owned assets
Owned assets:
Property and equipment, gross	30,306	29,030
Land | Owned assets
Owned assets:
Property and equipment, gross	135,808	135,871
Asset retirement obligations | Owned assets
Owned assets:
Property and equipment, gross	$ 31,965	$ 31,965

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Represents the compensation costs the entity capitalizes as a part of property, plant and equipment.

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Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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