GOODWILL, RADIO BROADCASTING LICENSES AND OTHER INTANGIBLE ASSETS - Valuation of Broadcasting Licenses (Details) - USD ($) $ in Millions	Dec. 31, 2020	Oct. 01, 2020	Sep. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Oct. 01, 2019	Mar. 31, 2018
Schedule of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Impairment charge (in millions)	$ 84.4				$ 10.6
Radio Broadcasting Licenses [Member]
Schedule of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Impairment charge (in millions)		$ 1.7	$ 19.1	$ 47.7		$ 1.0	$ 3.8
Discount Rate		9.00%	9.00%	9.50%		9.00%
Year 1 Market Revenue Growth Rate Range				(13.30%)
Radio Broadcasting Licenses [Member] | Maximum [Member]
Schedule of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Year 1 Market Revenue Growth Rate Range		(16.00%)	(16.80%)			1.80%
Long-term Market Revenue Growth Rate Range (Years 6 - 10)		1.10%	1.10%	1.10%		1.10%
Mature Market Share Range		23.90%	23.90%	25.00%		25.00%
Mature Operating Profit Margin Range		37.10%	37.10%	39.70%		39.70%
Radio Broadcasting Licenses [Member] | Minimum [Member]
Schedule of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Year 1 Market Revenue Growth Rate Range		(10.70%)	(10.70%)			0.90%
Long-term Market Revenue Growth Rate Range (Years 6 - 10)		0.70%	0.70%	0.70%		0.70%
Mature Market Share Range		6.70%	6.70%	6.90%		6.90%
Mature Operating Profit Margin Range		27.70%	27.70%	27.60%		27.60%