FAIR VALUE OF FINANCIAL INSTRUMENTS - Narrative (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Indefinite-lived Intangible Assets [Line Items]
Impairment charge on licenses									$ 261,929,000	$ 0
Goodwill impairment loss					$ 537,400,000				0	537,353,000	$ 317,138,000
Goodwill impairment loss, net of tax					519,600,000
Impairment charge related to ROU asset impairment				$ 1,100,000	6,000,000.0				1,064,000	5,956,000	0
Property and equipment and other	$ 1,400,000				2,200,000				$ 1,439,000	$ 2,148,000	$ 28,286,000
Impairment - Market Assets								$ 2,100,000
Impairment - Assets Held for Sale								26,900,000
Radio broadcasting licenses
Indefinite-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