GOODWILL, RADIO BROADCASTING LICENSES AND OTHER INTANGIBLE ASSETS (Details 2) - USD ($) $ in Millions		Dec. 31, 2017	Oct. 01, 2017	Dec. 31, 2016	Oct. 01, 2016
Schedule Of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Pre-tax impairment charge		$ 29.1		$ 1.3
Radio Marketing Units [Member]
Schedule Of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Pre-tax impairment charge	[1]		$ 0.0		$ 0.0
Discount Rate	[1]		9.00%		9.00%
Radio Marketing Units [Member] | Minimum [Member]
Schedule Of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Year 1 Market Revenue Growth Rate Range	[1]		(8.40%)		(9.40%)
Long-term Market Revenue Growth Rate Range (Years 6 - 10)	[1]		0.50%		0.50%
Mature Market Share Range	[1]		8.00%		8.10%
Mature Operating Profit Margin Range	[1]		25.10%		26.30%
Radio Marketing Units [Member] | Maximum [Member]
Schedule Of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Year 1 Market Revenue Growth Rate Range	[1]		46.60%		29.40%
Long-term Market Revenue Growth Rate Range (Years 6 - 10)	[1]		1.50%		1.50%
Mature Market Share Range	[1]		18.20%		18.40%
Mature Operating Profit Margin Range	[1]		50.10%		53.80%

[1] Reflects the key assumptions for testing only those radio markets with remaining goodwill.