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RELATED PERSON TRANSACTIONS - Cunningham Broadcasting Corporation (Details) $ in Thousands	1 Months Ended		3 Months Ended		9 Months Ended
	Aug. 31, 2016 USD ($)	Apr. 30, 2016 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) renewal	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Related Party Transaction [Line Items]
Total revenues			$ 766,260	$ 644,532	$ 2,161,756	$ 1,923,702
Repayments of debt					$ 154,244	318,309
Affiliated Entity \| Cunningham
Related Party Transaction [Line Items]
Right to acquire capital stock			100.00%		100.00%
Remaining purchase price			$ 53,600		$ 53,600
Purchase options, broadcast stations			200		$ 200
Proceeds from sale of master control equipment		$ 700
Annual revenue from master control services		$ 200
Annual revenue for share service	$ 1,000
Repayments of debt						19,500
Related party interest income				200		700
Affiliated Entity \| Cunningham \| LMA
Related Party Transaction [Line Items]
Number of additional renewal terms \| renewal					2
Agreement renewal period					5 years
Lease payments made to entities			$ 2,000	2,400	$ 6,700	6,400
Affiliated Entity \| Cunningham \| LMA \| Minimum
Related Party Transaction [Line Items]
Percentage of net broadcast revenue used to determine annual LMA fees required to be paid			3.00%		3.00%
Amount used to determine annual LMA fees required to be paid			$ 5,000		$ 5,000
Annual increase in aggregate purchase price			6.00%		6.00%
Cunningham license related assets \| Cunningham
Related Party Transaction [Line Items]
Agreement renewal period					8 years
Amount received			$ 19,700	6,600	$ 48,600	10,900
Total revenues			43,100	$ 31,400	119,500	$ 84,500
Guarantee Obligations
Related Party Transaction [Line Items]
Unconditional and irrevocably guaranteed debt			78,500		78,500		$ 74,000
Guarantee Obligations \| Affiliated Entity \| Cunningham
Related Party Transaction [Line Items]
Unconditional and irrevocably guaranteed debt			51,400		51,400
Consolidated VIEs \| Affiliated Entity \| Cunningham
Related Party Transaction [Line Items]
Long-term debt			10,300		10,300
Deferred financing costs			$ 700		$ 700