INTANGIBLE ASSETS AND GOODWILL - Changes in goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended	12 Months Ended
	Dec. 31, 2018	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Goodwill before cumulative loss on impairment	$ 982,663		$ 982,663	$ 988,056
Accumulated loss on impairment	443,194		443,194	$ 126,056
Beginning balance after cumulative loss on impairment		$ 539,469	862,000
Loss on impairment during the year	(317,100)		(317,138)
Measurement period adjustments to acquired goodwill			(21,498)
Ending balance	$ 539,469	536,687	539,469
Cumulus Exchange [Member]
Goodwill [Line Items]
Disposition of radio stations		(4,862)
WXTU Transaction disposition [Member]
Goodwill [Line Items]
Disposition of radio stations			(8,623)
Cumulus Exchange [Member]
Goodwill [Line Items]
Acquisition of rasdio stations		$ 2,080
Emmis Acquisition [Member]
Goodwill [Line Items]
Acquisition of rasdio stations			332
Jerry Lee Transaction [Member]
Goodwill [Line Items]
Acquisition of rasdio stations			$ 24,396