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Geographic and segment information: (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($) segment	Jun. 30, 2025 USD ($)	Dec. 31, 2025 USD ($)
Segment information
Number of operating segments \| segment			1
Revenues	$ 235,559	$ 246,247	$ 474,746	$ 493,298
Long lived assets, net	1,638,204		1,638,204		$ 1,721,074
On-net IP
Segment information
Revenues	135,368	132,331	270,935	261,961
Off-net IP
Segment information
Revenues	84,487	102,177	173,522	209,452
Wavelength
Segment information
Revenues	14,831	9,057	28,416	16,175
Non-core
Segment information
Revenues	873	2,682	1,873	5,710
North America
Segment information
Revenues	194,986	207,363	393,117	417,294
Long lived assets, net	1,438,639		1,438,639		1,523,789
North America \| On-net IP
Segment information
Revenues	100,488	100,102	200,920	199,183
North America \| Off-net IP
Segment information
Revenues	79,211	95,842	162,686	196,862
North America \| Wavelength
Segment information
Revenues	14,473	8,814	27,739	15,705
North America \| Non-core
Segment information
Revenues	814	2,605	1,772	5,544
Europe
Segment information
Revenues	30,609	30,546	62,032	59,545
Europe \| On-net IP
Segment information
Revenues	25,970	25,174	52,564	48,943
Europe \| Off-net IP
Segment information
Revenues	4,289	5,087	8,791	10,049
Europe \| Wavelength
Segment information
Revenues	316	231	600	447
Europe \| Non-core
Segment information
Revenues	34	54	77	106
South America
Segment information
Revenues	2,644	2,104	5,239	4,084
South America \| On-net IP
Segment information
Revenues	2,506	1,889	4,944	3,652
South America \| Off-net IP
Segment information
Revenues	132	207	284	415
South America \| Non-core
Segment information
Revenues	6	8	11	17
Oceania
Segment information
Revenues	7,166	6,081	14,005	12,084
Oceania \| On-net IP
Segment information
Revenues	6,263	5,038	12,185	9,943
Oceania \| Off-net IP
Segment information
Revenues	855	1,016	1,730	2,075
Oceania \| Wavelength
Segment information
Revenues	42	12	77	23
Oceania \| Non-core
Segment information
Revenues	6	15	13	43
Africa
Segment information
Revenues	154	153	353	291
Africa \| On-net IP
Segment information
Revenues	141	128	322	240
Africa \| Off-net IP
Segment information
Revenues		$ 25	31	$ 51
Africa \| Non-core
Segment information
Revenues	13
Europe and other
Segment information
Long lived assets, net	$ 199,565		$ 199,565		$ 197,285