BUSINESS COMBINATIONS - Preliminary purchase price allocations (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Jul. 19, 2019	May 09, 2019	Dec. 31, 2018	Sep. 27, 2018	Apr. 30, 2018	Dec. 31, 2017
Acquisition [Line Items]
Goodwill	$ 549,881			$ 539,469			$ 862,000
Pineapple Street Media [Member]
Acquisition [Line Items]
Accounts receivable		$ 997
Goodwill		12,445
Total intangible and other assets		15,235
Total assets		15,235
Accounts payable		30
Unearned revenue		238
Total liabilities		268
Preliminary fair value of net assets acquired		14,967
Pineapple Street Media [Member] | Brandname [Member]
Acquisition [Line Items]
Intangible Assets, Other than Goodwill		$ 1,793
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] | Advertising contracts [Member]
Acquisition [Line Items]
Intangible Assets, Other than Goodwill					477
2018 Jerry Lee Transaction [Member] | Radio broadcasting licenses [Member]
Acquisition [Line Items]
Intangible Assets, Other than Goodwill					$ 27,346