GOODWILL, RADIO BROADCASTING LICENSES AND OTHER INTANGIBLE ASSETS (Details) - USD ($) $ in Millions	Dec. 31, 2017	Oct. 01, 2017	Sep. 30, 2017		Jun. 30, 2017	[1]	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 Broadcasting Licenses [Member]
Schedule Of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Pre-tax impairment charge		$ 0.0	$ 16.4	[1]	$ 12.7			$ 1.3
Discount Rate		9.00%	9.00%	[1]	9.00%			9.00%
Minimum [Member] | Radio Broadcasting Licenses [Member]
Schedule Of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Year 1 Market Revenue Growth Rate Range		(5.00%)	(5.00%)	[1]	1.00%			1.00%
Long-term Market Revenue Growth Rate Range (Years 6 - 10)		0.50%	0.50%	[1]	0.50%			0.50%
Mature Market Share Range		6.80%	6.90%	[1]	6.90%			6.90%
Mature Operating Profit Margin Range		30.90%	31.00%		31.60%			30.50%
Maximum [Member] | Radio Broadcasting Licenses [Member]
Schedule Of Goodwill, Radio Broadcasting Licenses And Other Intangible Assets [Line Items]
Year 1 Market Revenue Growth Rate Range		1.40%	2.00%	[1]	2.00%			2.40%
Long-term Market Revenue Growth Rate Range (Years 6 - 10)		1.50%	1.50%	[1]	1.50%			1.50%
Mature Market Share Range		25.40%	25.80%	[1]	15.30%			25.80%
Mature Operating Profit Margin Range		46.90%	47.00%		47.00%			51.80%

[1] Reflects changes only to the key assumptions used in the interim testing for certain units of accounting.