Summary of Significant Accounting Policies - Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Property Plant and Equipment, Gross	$ 142,403	$ 140,220
Accumulated depreciation	(83,692)	(81,117)
Property, Plant and Equipment, Net, Total	58,711	59,103
Land and Land Improvements [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment, Gross	14,693	14,402
Building [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment, Gross	$ 37,984	35,812
Estimated Useful Life	31 years 6 months
Towers And Antennae [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment, Gross	$ 24,762	25,959
Towers And Antennae [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years
Towers And Antennae [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	15 years
Equipment [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment, Gross	$ 54,321	53,752
Equipment [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	3 years
Equipment [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	15 years
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment, Gross	$ 7,169	6,740
Furniture and Fixtures [Member] | Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	7 years
Furniture and Fixtures [Member] | Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated Useful Life	20 years
Vehicles [Member]
Property, Plant and Equipment [Line Items]
Property Plant and Equipment, Gross	$ 3,474	$ 3,555
Estimated Useful Life	5 years