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Geographic and segment information: (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2026 USD ($)	Sep. 30, 2025 USD ($)	Sep. 30, 2026 USD ($) segment	Sep. 30, 2025 USD ($)	Dec. 31, 2025 USD ($)
Segment information
Number of operating segments \| segment			1
Revenues	$ 231,203	$ 241,949	$ 705,948	$ 735,242
Long lived assets, net	1,626,018		1,626,018		$ 1,721,074
On-net
Segment information
Revenues	137,887	135,267	408,824	397,225
Off-net
Segment information
Revenues	76,593	95,111	250,114	304,558
Wavelength
Segment information
Revenues	15,983	10,179	44,398	26,356
Non-core
Segment information
Revenues	740	1,392	2,612	7,103
North America
Segment information
Revenues	191,692	202,228	584,809	619,520
Long lived assets, net	1,427,089		1,427,089		1,523,789
North America \| On-net
Segment information
Revenues	103,795	101,746	304,717	300,927
North America \| Off-net
Segment information
Revenues	71,660	89,227	234,345	286,086
North America \| Wavelength
Segment information
Revenues	15,534	9,934	43,273	25,641
North America \| Non-core
Segment information
Revenues	703	1,321	2,474	6,866
Europe
Segment information
Revenues	29,418	30,965	91,450	90,510
Europe \| On-net
Segment information
Revenues	24,987	25,904	77,551	74,847
Europe \| Off-net
Segment information
Revenues	4,033	4,773	12,824	14,822
Europe \| Wavelength
Segment information
Revenues	370	233	970	680
Europe \| Non-core
Segment information
Revenues	28	55	105	161
South America
Segment information
Revenues	2,842	2,311	8,081	6,395
South America \| On-net
Segment information
Revenues	2,713	2,158	7,657	5,810
South America \| Off-net
Segment information
Revenues	124	148	408	563
South America \| Non-core
Segment information
Revenues	5	5	16	22
Oceania
Segment information
Revenues	7,097	6,291	21,101	18,373
Oceania \| On-net
Segment information
Revenues	6,251	5,331	18,436	15,273
Oceania \| Off-net
Segment information
Revenues	763	937	2,493	3,011
Oceania \| Wavelength
Segment information
Revenues	79	12	155	35
Oceania \| Non-core
Segment information
Revenues	4	11	17	54
Africa
Segment information
Revenues	154	154	507	444
Africa \| On-net
Segment information
Revenues	141	128	463	368
Africa \| Off-net
Segment information
Revenues	13	$ 26	44	$ 76
Europe and other
Segment information
Long lived assets, net	$ 198,929		$ 198,929		$ 197,285