INTANGIBLE ASSETS AND GOODWILL - Narrative (Details)	3 Months Ended							12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) radioMarket	Dec. 31, 2018 USD ($) radioMarket	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2020 USD ($) years	Dec. 31, 2019 USD ($) radioMarket	Dec. 31, 2018 USD ($) radioMarket	Nov. 30, 2017 radioMarket	Oct. 31, 2017 radioMarket
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment testing window								3 years
Impairment charge on licenses								$ 261,929,000	$ 0
Goodwill impairment loss				$ 537,400,000				$ 0	$ 537,353,000	$ 317,138,000
Income model years | years								10
Number of radio markets | radioMarket				47	48				47	48	48	28
Goodwill impairment loss, net of tax				$ 519,600,000
Radio broadcasting licenses
Finite-Lived Intangible Assets [Line Items]
Impairment charge on licenses	$ 246,000,000.0	$ 11,800,000	$ 4,100,000	$ 0	$ 147,900,000	$ 700,000	$ 0
Impairment charge on licenses, net of tax	180,400,000	$ 8,700,000	$ 3,000,000.0		108,800,000
Goodwill
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment loss					317,100,000		$ 0
Goodwill impairment loss, net of tax					$ 314,400,000
Podcasting Reporting Unit
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment loss	$ 0							$ 0