Goodwill and Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Finite-Lived Intangible Assets [Line Items]
Non-amortizing intangibles	$ 94,433	$ 78,314
Gross carrying amount	35,699	33,187
Accumulated amortization and other	(26,617)	(25,947)
Total	9,082	7,240
Total intangible assets, gross carrying amount	133,376	114,188
Intangible assets, net	106,759	88,241
Broadband
Finite-Lived Intangible Assets [Line Items]
Goodwill, gross	3,244	2,687
Goodwill	3,244	2,687
FCC spectrum licenses
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	6,811	4,659
Accumulated amortization and other	(340)	(97)
Total	6,471	4,562
Subscriber relationships
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	28,425	28,065
Accumulated amortization and other	(26,000)	(25,600)
Total	2,425	2,465
Other intangibles
Finite-Lived Intangible Assets [Line Items]
Gross carrying amount	463	463
Accumulated amortization and other	(277)	(250)
Total	186	213
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	13,839
Railroad crossing rights
Finite-Lived Intangible Assets [Line Items]
Non-amortizing intangibles	$ 141	$ 141