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Summary of Significant Accounting Policies - Additional Information (Details)
Mar. 31, 2021
USD ($)
RadioStation
Structure
Dec. 31, 2020
USD ($)
Significant Accounting Policies [Line Items]    
Number of radio stations | RadioStation 2  
Number of advertising structures | Structure 3,500  
Deferred tax assets valuation allowance $ 18,800,000  
COVID-19    
Significant Accounting Policies [Line Items]    
Deferred tax assets valuation allowance   $ 18,800,000
Fair Value Measurements Recurring | Level 3    
Significant Accounting Policies [Line Items]    
Assets 0  
Liabilities $ 0