BUSINESS COMBINATIONS - Preliminary purchase price allocations (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	May 09, 2019	Dec. 31, 2018	Sep. 27, 2018	Apr. 30, 2018	Dec. 31, 2017
Acquisition [Line Items]
Goodwill	$ 536,687		$ 539,469			$ 862,000
2019 Cumulus Exchange [Member]
Acquisition [Line Items]
Total tangible property		$ 844
Goodwill		2,080
Total intangible and other assets		21,656
Total assets		22,500
Preliminary fair value of net assets acquired		22,500
2019 Cumulus Exchange [Member] | Equipment [Member]
Acquisition [Line Items]
Total tangible property		844
2019 Cumulus Exchange [Member] | Equipment [Member] | Minimum [Member]
Acquisition [Line Items]
Useful lives in years	3 years
2019 Cumulus Exchange [Member] | Equipment [Member] | Maximum [Member]
Acquisition [Line Items]
Useful lives in years	7 years
2019 Cumulus Exchange [Member] | Radio broadcasting licenses [Member]
Acquisition [Line Items]
Intangible Assets, Other than Goodwill		$ 19,576
2018 Emmis Acquisition [Member]
Acquisition [Line Items]
Total tangible property					$ 1,558
Goodwill					332
Other noncurrent assets					4
Total intangible and other assets					13,442
Total assets					15,000
Preliminary fair value of net assets acquired					15,000
2018 Emmis Acquisition [Member] | Equipment [Member]
Acquisition [Line Items]
Total tangible property					1,558
2018 Emmis Acquisition [Member] | Advertising contracts [Member]
Acquisition [Line Items]
Intangible Assets, Other than Goodwill					114
2018 Emmis Acquisition [Member] | Radio broadcasting licenses [Member]
Acquisition [Line Items]
Intangible Assets, Other than Goodwill					12,785
2018 Emmis Acquisition [Member] | Advertiser relationships [Member]
Acquisition [Line Items]
Intangible Assets, Other than Goodwill					$ 207
2018 Jerry Lee Transaction [Member]
Acquisition [Line Items]
Total tangible property				$ 981
Goodwill				24,396
Net working capital acquired				3,234
Total intangible and other assets				55,453
Total assets				56,434
Preliminary fair value of net assets acquired				56,434
2018 Jerry Lee Transaction [Member] | Equipment [Member]
Acquisition [Line Items]
Total tangible property				981
2018 Jerry Lee Transaction [Member] | Equipment [Member] | Minimum [Member]
Acquisition [Line Items]
Useful lives in years	3 years
2018 Jerry Lee Transaction [Member] | Equipment [Member] | Maximum [Member]
Acquisition [Line Items]
Useful lives in years	7 years
2018 Jerry Lee Transaction [Member] | Advertising contracts [Member]
Acquisition [Line Items]
Intangible Assets, Other than Goodwill				477
2018 Jerry Lee Transaction [Member] | Advertising contracts [Member] | Minimum [Member]
Acquisition [Line Items]
Useful lives in years	1 year
2018 Jerry Lee Transaction [Member] | Advertising contracts [Member] | Maximum [Member]
Acquisition [Line Items]
Useful lives in years	1 year
2018 Jerry Lee Transaction [Member] | Radio broadcasting licenses [Member]
Acquisition [Line Items]
Intangible Assets, Other than Goodwill				$ 27,346