Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Summary of Depreciation Using the Straight-line Method over Estimated Useful Lives (Detail)

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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