Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Finite-Lived Intangible Assets [Line Items]
Non-amortizing intangibles	$ 94,433	$ 94,433
Gross carrying amount	35,699	35,699
Accumulated amortization and other	(26,833)	(26,617)
Total	8,866	9,082
Total intangible assets, gross carrying amount	133,376	133,376
Intangible assets, net	106,543	106,759
Broadband
Finite-Lived Intangible Assets [Line Items]
Goodwill, gross	3,244	3,244
Goodwill	3,244	3,244
FCC spectrum licenses
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	6,811	6,811
Accumulated amortization and other	(437)	(340)
Total	6,374	6,471
Subscriber relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	28,425	28,425
Accumulated amortization and other	(26,113)	(26,000)
Total	2,312	2,425
Other intangibles
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	463	463
Accumulated amortization and other	(283)	(277)
Total	180	186
Cable franchise rights
Finite-Lived Intangible Assets [Line Items]
Non-amortizing intangibles	64,334	64,334
FCC spectrum licenses
Finite-Lived Intangible Assets [Line Items]
Non-amortizing intangibles	29,958	29,958
Railroad crossing rights
Finite-Lived Intangible Assets [Line Items]
Non-amortizing intangibles	$ 141	$ 141