Property and Equipment - Property and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 254,600	$ 258,900
Less accumulated depreciation	191,183	188,579
Property and equipment excluding land, net	63,400	70,300
Land	8,600	9,300
Property and equipment, total	72,004	79,642
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 19,700	21,900
Property and equipment, Estimated useful life	40 years
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 1,900	15,100
Transmission, studio and other broadcast equipment
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 170,300	162,100
Transmission, studio and other broadcast equipment | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	5 years
Transmission, studio and other broadcast equipment | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	15 years
Office and computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 33,900	31,400
Office and computer equipment | Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	3 years
Office and computer equipment | Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, Estimated useful life	7 years
Transportation equipment
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 6,800	6,300
Property and equipment, Estimated useful life	5 years
Leasehold improvements and land improvements
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 22,000	$ 22,100
Property and equipment, Estimated useful life	Lesser of lease life or useful life