FAIR VALUE OF FINANCIAL INSTRUMENTS - Narrative (Details) - USD ($)		3 Months Ended				12 Months Ended
	Oct. 16, 2019	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jul. 31, 2017
Indefinite-lived Intangible Assets [Line Items]
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
Impairment charge on licenses						0	148,564,000
Property and equipment and other		2,200,000				2,148,000	28,286,000	511,000
Impairment - Market Assets					$ 2,100,000
Impairment - Assets Held for Sale					26,900,000
Business Acquisition [Line Items]
Payments to acquire restricted investments						1,800,000	1,250,000
Impairment charge related to ROU asset impairment		6,000,000.0				$ 5,956,000	$ 0	$ 0
Radio broadcasting licenses
Indefinite-lived Intangible Assets [Line Items]
Impairment charge on licenses		0		147,900,000	$ 0
Impairment charge on licenses, net of tax				$ 108,800,000
AnalyticOwl
Business Acquisition [Line Items]
Payments to acquire restricted investments			$ 1,500,000
The Action Network
Business Acquisition [Line Items]
Payments to acquire restricted investments		$ 300,000
Cadence 13
Business Acquisition [Line Items]
Percentage of equity interest prior to acquisition									45.00%
Recognized gain on previously held equity interest	$ 5,300,000