ACQUISITIONS AND DISPOSITIONS OF ASSETS - Narrative (Details) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 01, 2017 USD ($) station market	Sep. 30, 2018 USD ($) station market	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) station market	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Business Acquisition [Line Items]
Number of television stations owned | station		191		191
Number of markets | market		89		89
Broadcast incentive auction, proceeds				$ 310,800
Gain (loss) on sale of assets and asset impairment charges		$ 10,828	$ 34	$ 36,678	$ 53,531
Number of stations assigned new channels | station				100
Broadcast incentive auction, total legislation funds to reimburse stations				$ 2,750,000
Broadcast incentive auction, total capital expenditure		9,200		20,900
Asset impairment charges				59,600
Bonten
Business Acquisition [Line Items]
Aggregate purchase price	$ 240,000
Working capital adjustment	$ 2,200
Number of television stations owned | station	14
Number of markets | market	8
Number of stations to which sales services were provided | station	4
Measurement period adjustments, increase to goodwill				1,500
Finite-lived intangible assets acquired	$ 161,900
Goodwill, expected to be deductible for tax purposes	5,600
Net revenues		25,900	7,600	71,300	7,600
Operating income (loss)		6,000	$ 900	11,700	$ 900
Bonten | Network Affiliations
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 53,300
Acquired finite-lived intangible assets, weighted average useful life	15 years
Bonten | Customer relationships
Business Acquisition [Line Items]
Finite-lived intangible assets acquired	$ 108,600
Acquired finite-lived intangible assets, weighted average useful life	14 years
Other Acquisitions
Business Acquisition [Line Items]
Working capital adjustment						$ 2,700
Business combination purchase price						$ 27,400
Tribune Media Company
Business Acquisition [Line Items]
Acquisition related costs		33,500		99,700
General and Administrative Expense | Tribune Media Company
Business Acquisition [Line Items]
Acquisition related costs		11,300		21,200
Interest Expense | Tribune Media Company
Business Acquisition [Line Items]
Acquisition related costs		$ 22,200		78,500
Spectrum Auction
Business Acquisition [Line Items]
Gain (loss) on sale of assets and asset impairment charges				$ 83,300