Revenues - Summary of Disaggregation of Broadcast Advertising Revenue by Sales Channel (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation Of Revenue [Line Items]
Total revenue	$ 178,410	$ 45,116	$ 327,290	$ 109,365
Advertising
Disaggregation Of Revenue [Line Items]
Total revenue	36,438	22,589	70,113	61,317
Advertising | Local Direct
Disaggregation Of Revenue [Line Items]
Total revenue	5,729	4,093	10,969	9,936
Advertising | Local Agency
Disaggregation Of Revenue [Line Items]
Total revenue	15,219	7,873	28,407	21,439
Advertising | National Agency
Disaggregation Of Revenue [Line Items]
Total revenue	$ 15,490	$ 10,623	$ 30,737	$ 29,942