Description of the business and recent developments: Leases (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Finance leases-fiber lease agreements
Initial terms	22 years		22 years
Additional finance lease future payments due	$ 172,500		$ 172,500
Cash paid for amounts included in the measurement of lease liabilities
Amortization of right-of-use assets	7,000	$ 6,378	13,998	$ 12,724
Interest expense on finance lease liabilities	5,116	4,685	10,197	9,911
Operating lease cost	4,628	4,671	9,401	9,088
Total lease costs	$ 16,744	$ 15,734	33,596	31,723
Operating cash flows from finance leases			(11,083)	(10,111)
Operating cash flows from operating leases			(9,543)	(10,104)
Financing cash flows from finance leases			(11,099)	(11,936)
Right-of-use assets obtained in exchange for new finance lease liabilities			23,685	16,218
Right-of-use assets obtained in exchange for new operating lease liabilities			$ 9,429	$ 12,531
Weighted-average remaining lease term - finance leases (in years)	12 years 8 months 12 days	12 years 6 months	12 years 8 months 12 days	12 years 6 months
Weighted-average remaining lease term - operating leases (in years)	18 years 1 month 6 days	19 years 4 months 24 days	18 years 1 month 6 days	19 years 4 months 24 days
Weighted average discount rate - finance leases	8.70%	9.80%	8.70%	9.80%
Weighted average discount rate - operating leases	5.40%	5.50%	5.40%	5.50%
Future minimum payments (principal and interest) under these finance leases
2022	$ 37,002		$ 37,002
2023	36,498		36,498
2024	36,162		36,162
2025	29,062		29,062
2026	29,013		29,013
Thereafter	259,294		259,294
Total minimum lease obligations	427,031		427,031
Less-amounts representing interest	(172,817)		(172,817)
Present value of minimum lease obligations	254,214		254,214
Current maturities	(17,562)		(17,562)		$ (17,048)
Finance lease obligations, net of current maturities	236,652		236,652		228,822
Future minimum payments under these operating lease agreements
2022	18,071		18,071
2023	18,078		18,078
2024	16,862		16,862
2025	14,332		14,332
2026	12,551		12,551
Thereafter	107,376		107,376
Total minimum lease obligations	187,270		187,270
Less-amounts representing interest	(64,363)		(64,363)
Present value of minimum lease obligations	122,907		122,907
Current maturities	(12,172)		(12,172)		(12,197)
Lease obligations, net of current maturities	$ 110,735		$ 110,735		$ 111,794
Minimum
Finance leases-fiber lease agreements
Initial terms	15 years		15 years
Maximum
Finance leases-fiber lease agreements
Initial terms	20 years		20 years