Property and Equipment - Property and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 230,900	$ 251,500
Less accumulated depreciation	179,869	204,343
Property and equipment excluding land, net	51,000	47,200
Land	9,300	8,200
Property and equipment, total	60,337	55,368
Buildings
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 22,400	18,600
Property and equipment, Estimated useful life	39 years
Construction in progress
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 4,600	2,600
Transmission, studio and other broadcast equipment
Property, Plant and Equipment [Line Items]
Property and equipment excluding land gross	$ 145,900	166,900
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	$ 28,900	30,200
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	$ 6,400	6,800
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	$ 22,700	$ 26,400
Property and equipment, Estimated useful life	Lesser of lease life or useful life