INTANGIBLE ASSETS AND GOODWILL (Details) $ in Thousands	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($) number	Jun. 30, 2017 number	Jun. 30, 2018 USD ($) number	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Changes in broadcasting licenses [Line Items]
Beginning of period balance			$ 2,649,959	$ 823,195
Consolidation of a VIE			0	(15,738)
Impairment loss			(702)	0
Acquisition of radio stations			0	17,174
Disposition of Licenses - EMF Sale			0	(54,661)
Acqusition of radio Stations - Beasley Transaction			0	35,944
Acquisition of radio stations - iHeartMedia Transaction			0	50,621
Disposition of radio stations - iHeartMedia Transaction			0	(7,462)
Assets held for sale			0	(66,014)
Deconsolidation of a subsidiary			0	0
Acquisition - other			0	0
Dispositions			0	(13,500)
Acquisition of radio stations - Emmis Acquisition			332	0
Indefinitelived Intangible Assets Acquired Through Exchange			0	0
Ending period balance	$ 2,662,042		$ 2,662,042	2,649,959
Market approach for step one goodwill analysis [Abstract]
Income model years used for the discounted cash flow approach | number			10
Changes in goodwill [Roll Forward]
Goodwill before cumulative loss on impairment				988,056	$ 158,333
Accumulated loss on impairment				(126,056)	$ (125,615)
Beginning balance after cumulative loss on impairment			$ 862,000	32,718
Loss on impairment during the year			0	(441)
Acquisition			0	820,961
Acquisition of Charlotte			0	43
Disposition of radio station - EMF sale			0	(266)
Acquisition of radio station - iHeartMedia Transaction			0	11,700
Disposition of radio station - iHeartMedia Transaction			0	(14)
Adjustments to acquired goodwill			(4,401)	0
Acquisition of radio station - Beasley Transaction			0	289
Assets held for sale			0	(2,990)
Deconsolidation of a subsidiary			0	0
Goodwill Acquired Through Exchange			0	0
Ending balance	$ 857,931		857,931	862,000
Acquisition of radio stations - Emmis Acquisition			332	0
Broadcasting License Impairment Testing [Member]
Estimates and assumptions used for impairment test [Line Items]
Discount rates	9.00%	9.25%
Broadcasting License Impairment Testing [Member] | Maximum [Member]
Estimates and assumptions used for impairment test [Line Items]
Operating profit margin ranges of the markets of the Company	37.00%	40.00%
Long-term revenue growth rate ranges of the markets of the Company	1.00%	2.00%
Broadcasting License Impairment Testing [Member] | Minimum [Member]
Estimates and assumptions used for impairment test [Line Items]
Operating profit margin ranges of the markets of the Company	22.00%	19.00%
Long-term revenue growth rate ranges of the markets of the Company	0.50%	1.00%
Goodwill Impairment Testing [Member]
Estimates and assumptions used for impairment test [Line Items]
Discount rates	9.00%	9.25%
Goodwill Impairment Testing [Member] | Maximum [Member]
Estimates and assumptions used for impairment test [Line Items]
Long-term revenue growth rate ranges of the markets of the Company	1.00%	2.00%
Market approach for step one goodwill analysis [Abstract]
Estimates of market multiples | number	0	8
Goodwill Impairment Testing [Member] | Minimum [Member]
Estimates and assumptions used for impairment test [Line Items]
Long-term revenue growth rate ranges of the markets of the Company	1.00%	1.00%
Market approach for step one goodwill analysis [Abstract]
Estimates of market multiples | number	0	7.5
Radio Broadcasting Licences [Member]
Changes in broadcasting licenses [Line Items]
Acquisition of radio stations - CBS Radio Merger			0	1,880,400
Acquisition of radio stations - Emmis Acquisition			12,785	0
Changes in goodwill [Roll Forward]
Acquisition of radio stations - Emmis Acquisition			$ 12,785	$ 0