Impairment of FCC Broadcasting Licenses - Summary of Key Assumptions Used in Impairment Assessment Using Significant Unobservable Inputs (Details) - Level 3 - Discounted Cash Flow Methodology - Fair Value, Measurements, Nonrecurring	Jun. 30, 2018
Discount Rate | Radio FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative investment, measurement input	9.5
Discount Rate | Television FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative investment, measurement input	12.0
Long-term Revenue Growth Rate | Television FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative investment, measurement input	0.5
Mature Market Share | Television FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative investment, measurement input	2.0
Mature Operating Profit Margin | Radio FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative investment, measurement input	30.1
Mature Operating Profit Margin | Television FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative investment, measurement input	24.0
Minimum | Long-term Revenue Growth Rate | Radio FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative investment, measurement input	1.0
Minimum | Mature Market Share | Radio FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative investment, measurement input	2.7
Maximum | Long-term Revenue Growth Rate | Radio FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative investment, measurement input	1.5
Maximum | Mature Market Share | Radio FCC Licenses
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]
Alternative investment, measurement input	4.4