INTANGIBLE ASSETS AND GOODWILL - Narrative (Details)	3 Months Ended			12 Months Ended
	Dec. 31, 2019 USD ($) radioMarket	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) radioMarket	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($) radioMarket	Nov. 17, 2017 radioMarket	Nov. 01, 2017 radioMarket	Oct. 31, 2017 radioMarket
Finite-Lived Intangible Assets [Line Items]
Impairment charge on licenses				$ 0	$ 148,564,000
Number of radio markets | radioMarket	47			47		48	28	48	28
Goodwill impairment loss	$ 537,400,000	$ 317,100,000		$ 537,353,000	$ 317,138,000	$ 441,000
Goodwill impairment loss, net of tax	519,600,000	314,400,000
Income model years				10
Radio broadcasting licenses
Finite-Lived Intangible Assets [Line Items]
Impairment charge on licenses	$ 0	147,900,000	$ 0
Impairment charge on licenses, net of tax		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