Property and Equipment - Property and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 243,000	$ 230,900
Less accumulated depreciation	187,375	179,869
Property and equipment excluding land, net	55,600	51,000
Land	9,300	9,300
Property and equipment, total	64,939	60,337
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 21,800	22,400
Property and equipment, Estimated useful life	39 years
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 10,000	4,600
Transmission, studio and other broadcast equipment
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 151,300	145,900
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	$ 30,600	28,900
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	$ 6,300	6,400
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	$ 23,000	$ 22,700
Property and equipment, Estimated useful life	Lesser of lease life or useful life