The Company and Significant Accounting Policies - Carrying Amount of Goodwill (Detail) - USD ($)	3 Months Ended			9 Months Ended	12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill, Beginning balance			$ 46,511,000	$ 46,511,000
Impairment	$ 0	$ 0		(800,000)
Goodwill, Ending balance	45,711,000			45,711,000	$ 46,511,000
Television
Goodwill [Line Items]
Goodwill, Beginning balance			40,549,000	40,549,000
Impairment			0
Goodwill, Ending balance	40,549,000			40,549,000	40,549,000
Radio
Goodwill [Line Items]
Goodwill, Ending balance	0			0
Digital
Goodwill [Line Items]
Goodwill, Beginning balance			5,962,000	5,962,000
Impairment			$ (800,000)	(800,000)	(27,700,000)
Goodwill, Ending balance	$ 5,162,000			$ 5,162,000	$ 5,962,000