GOODWILL, RADIO BROADCASTING LICENSES AND OTHER INTANGIBLE ASSETS - Radio Market Reporting Units (Details) - USD ($) $ in Millions	Dec. 31, 2019	Oct. 01, 2019	Dec. 31, 2018	Oct. 01, 2018	Mar. 31, 2018
Schedule of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Impairment charge (in millions)	$ 10.6		$ 21.3
Radio Market Reporting Units [Member]
Schedule of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Impairment charge (in millions)		$ 0.0		$ 14.7	$ 2.7
Discount Rate		9.00%		9.00%
Radio Market Reporting Units [Member] | Minimum [Member]
Schedule of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Year 1 Market Revenue Growth Rate Range		(7.60%)		(8.00%)
Long-term Market Revenue Growth Rate Range (Years 6 - 10)		0.70%		0.70%
Mature Market Share Range		7.10%		7.60%
Mature Operating Profit Margin Range		26.80%		26.80%
Radio Market Reporting Units [Member] | Maximum [Member]
Schedule of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Year 1 Market Revenue Growth Rate Range		49.30%		27.50%
Long-term Market Revenue Growth Rate Range (Years 6 - 10)		1.10%		1.10%
Mature Market Share Range		17.00%		17.80%
Mature Operating Profit Margin Range		47.60%		46.90%