NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition, Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Disaggregation of Revenue [Line Items]
Total revenues	$ 665,352	$ 626,936
Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	595,892	569,869
Other
Disaggregation of Revenue [Line Items]
Total revenues	69,460	57,067
Advertising revenue, net of agency commissions
Disaggregation of Revenue [Line Items]
Total revenues	316,328	318,450
Advertising revenue, net of agency commissions | Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	298,912	310,071
Advertising revenue, net of agency commissions | Other
Disaggregation of Revenue [Line Items]
Total revenues	17,416	8,379
Distribution revenue
Disaggregation of Revenue [Line Items]
Total revenues	314,360	275,914
Distribution revenue | Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	287,125	249,065
Distribution revenue | Other
Disaggregation of Revenue [Line Items]
Total revenues	27,235	26,849
Other media and non-media revenues
Disaggregation of Revenue [Line Items]
Total revenues	34,664	32,572
Other media and non-media revenues | Broadcast
Disaggregation of Revenue [Line Items]
Total revenues	9,855	10,733
Other media and non-media revenues | Other
Disaggregation of Revenue [Line Items]
Total revenues	$ 24,809	$ 21,839