NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition, Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenues	$ 766,260	$ 644,532	$ 2,161,756	$ 1,923,702
Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	678,671	584,941	1,916,844	1,745,777
Other
Disaggregation of Revenue [Line Items]
Total revenues	87,589	59,591	244,912	177,925
Advertising revenue
Disaggregation of Revenue [Line Items]
Total revenues	385,246	330,986	1,060,697	992,084
Advertising revenue | Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	365,617	314,930	1,002,734	953,254
Advertising revenue | Other
Disaggregation of Revenue [Line Items]
Total revenues	19,629	16,056	57,963	38,830
Distribution revenue
Disaggregation of Revenue [Line Items]
Total revenues	330,693	285,358	964,511	839,987
Distribution revenue | Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	302,780	258,841	881,836	759,632
Distribution revenue | Other
Disaggregation of Revenue [Line Items]
Total revenues	27,913	26,517	82,675	80,355
Other media and non-media revenues
Disaggregation of Revenue [Line Items]
Total revenues	50,321	28,188	136,548	91,631
Other media and non-media revenues | Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	10,274	11,170	32,274	32,891
Other media and non-media revenues | Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 40,047	$ 17,018	$ 104,274	$ 58,740