Goodwill and Other Intangible Assets - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Oct. 01, 2017 USD ($)
Goodwill [Line Items]
Aggregate amortization expense	$ 5,900,000	$ 3,500,000	$ 3,500,000
Number of reporting segments | Segment	3
Goodwill	$ 70,557,000	50,081,000	50,081,000
FCC
Goodwill [Line Items]
Impairment of goodwill	0	0
Television
Goodwill [Line Items]
Impairment of goodwill	0	0	0
Goodwill	40,549,000	35,912,000	35,912,000
Digital
Goodwill [Line Items]
Impairment of goodwill	0
Goodwill	$ 30,008,000	14,169,000	$ 14,169,000	$ 30,000,000
Goodwill, impaired, method for fair value determination	the digital reporting unit fair value exceeded its carrying value by 1%, resulting in no impairment charge in 2017. The discount rate used in the fair value calculation of the digital reporting unit was increased from prior year and expected cash flows of a component of the reporting unit were decreased from prior year to account for risk within the forecasts of the reporting unit. If that discount rate were to increase by 1%, the fair value of the digital reporting unit would decrease by 6%. If the long term projected growth rate were to decrease by 0.5%, the fair value of the digital reporting unit would decrease by 1%.
Percentage of fair value of assets	1.00%
Radio
Goodwill [Line Items]
Goodwill	$ 0	$ 0