NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Revenue Recognition, Effects of Adoption (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 766,260	$ 644,532	$ 2,161,756	$ 1,923,702
Media production expenses	303,782	268,330	893,189	796,218
Operating income (loss)	157,810	103,447	396,707	379,924
Net income	$ 63,875	$ 30,637	$ 135,040	$ 132,483
Basic earnings per share (USD per share)	$ 0.63	$ 0.30	$ 1.32	$ 1.34
Diluted earnings per share (USD per share)	$ 0.62	$ 0.30	$ 1.31	$ 1.32
Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating income (loss)		$ 103,447		$ 379,924
Net income		$ 30,637		$ 132,483
Basic earnings per share (USD per share)		$ 0.30		$ 1.34
Diluted earnings per share (USD per share)		$ 0.30		$ 1.32
Restatement Adjustment | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating income (loss)		$ 0		$ 0
Net income		$ 0		$ 0
Basic earnings per share (USD per share)		$ 0		$ 0
Diluted earnings per share (USD per share)		$ 0		$ 0
Station Barter Arrangements
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues		$ 5,428		$ 15,404
Media production expenses		337		1,078
Station Barter Arrangements | Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues		31,787		91,817
Media production expenses		26,696		77,491
Station Barter Arrangements | Restatement Adjustment | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues		(26,359)		(76,413)
Media production expenses		$ (26,359)		$ (76,413)