Summary of Significant Accounting Policies - Summary of Depreciation Using the Straight-line Method over Estimated Useful Lives (Detail)	12 Months Ended
	Dec. 31, 2020
Building [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	40 years
Computer Software and Website Development Costs [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	3 years
Record and Tape Libraries [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	3 years
Automobiles [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	5 years
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment, description	Lesser of the useful life or remaining lease term
Minimum [Member] | Office Furnishings and Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	5 years
Minimum [Member] | Antennae, Towers and Transmitting Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	10 years
Minimum [Member] | Studio, Production and Mobile Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	5 years
Maximum [Member] | Office Furnishings and Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	10 years
Maximum [Member] | Antennae, Towers and Transmitting Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	20 years
Maximum [Member] | Studio, Production and Mobile Equipment [Member]
Property, Plant and Equipment [Line Items]
Estimated useful life of property and equipment	7 years