NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition, Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Total revenues	$ 730,143	$ 652,234	$ 1,395,496	$ 1,279,170
Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	642,279	590,967	1,238,172	1,160,836
Other
Disaggregation of Revenue [Line Items]
Total revenues	87,864	61,267	157,324	118,334
Advertising revenue, net of agency commissions
Disaggregation of Revenue [Line Items]
Total revenues	359,122	342,646	675,450	661,097
Advertising revenue, net of agency commissions | Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	338,204	328,252	637,116	638,323
Advertising revenue, net of agency commissions | Other
Disaggregation of Revenue [Line Items]
Total revenues	20,918	14,394	38,334	22,774
Distribution revenue
Disaggregation of Revenue [Line Items]
Total revenues	319,458	278,719	633,818	554,630
Distribution revenue | Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	291,931	251,730	579,056	500,792
Distribution revenue | Other
Disaggregation of Revenue [Line Items]
Total revenues	27,527	26,989	54,762	53,838
Other media and non-media revenues
Disaggregation of Revenue [Line Items]
Total revenues	51,563	30,869	86,228	63,443
Other media and non-media revenues | Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	12,144	10,985	22,000	21,721
Other media and non-media revenues | Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 39,419	$ 19,884	$ 64,228	$ 41,722