Acquisitions and Dispositions - 2019 Merger with Tribune - Additional Information (Details) $ / shares in Units, $ in Thousands				3 Months Ended				9 Months Ended		12 Months Ended
		Sep. 17, 2020 USD ($)	Sep. 19, 2019 USD ($) TelevisionStation Market RadioStation Station $ / shares	Sep. 30, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2019 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Dec. 31, 2019 $ / shares
Business Acquisition [Line Items]
Gain (Loss) on sale of business							$ 96,608	$ 7,025	$ 96,608
Increase (decrease) in goodwill								(87,000)
Consideration received from measurement period adjustment				$ 98,000				98,000
Income tax payable				30,000				30,000
Estimated fair value of equity investments			$ 1,447,000
Operating income				$ 343,597			121,615	$ 844,865	398,633
Network affiliation agreements [Member]
Business Acquisition [Line Items]
Network affiliation agreements useful life								15 years		15 years
Other definite-lived intangible assets [Member]
Business Acquisition [Line Items]
Weighted average estimated useful life of intangible assets								9 years
Other definite-lived intangible assets [Member] | Minimum [Member]
Business Acquisition [Line Items]
Network affiliation agreements useful life								1 year		1 year
Other definite-lived intangible assets [Member] | Maximum [Member]
Business Acquisition [Line Items]
Network affiliation agreements useful life								20 years		20 years
Senior Subordinated Notes [Member] | 5.625 % Due 2027 [Member]
Business Acquisition [Line Items]
Interest rate				5.625%	5.625%	5.625%		5.625%		5.625%
Class A Common Stock [Member]
Business Acquisition [Line Items]
Common stock, par value | $ / shares				$ 0.01	$ 0.01	$ 0.01		$ 0.01		$ 0.01
Class B Common Stock [Member]
Business Acquisition [Line Items]
Common stock, par value | $ / shares				$ 0.01	$ 0.01	$ 0.01		$ 0.01		$ 0.01
WGN America [Member] | Television Food Network and Portfolio of Real Estate Assets [Member]
Business Acquisition [Line Items]
Ownership stake			31.30%
TV Food Network [Member]
Business Acquisition [Line Items]
Ownership stake			31.30%	31.30%				31.30%
Tribune [Member]
Business Acquisition [Line Items]
Acquisition date			Sep. 19, 2019
Number of full power stations acquired | TelevisionStation			31
Number of AM radio stations acquired | RadioStation			1
Number of television market of stations acquired | Market			23
Number of stations divested | TelevisionStation			21
Number of television market of stations sold | Market			16
Outstanding equity acquired, price per share | $ / shares			$ 46.687397
Selling price of entities sold			$ 1,360,000
Business combination increase (decrease) in property and equipment						$ (8,900)
Business combination increase (decrease) in FCC licenses						(172,200)
Business combination increase (decrease) in network affiliation agreements						34,800
Business combination increase (decrease) in other intangible assets						252,000
Business combination increase (decrease) in deferred tax liabilities						(9,400)		$ (2,400)
Business combination increase (decrease) in long term liabilities						(8,000)
Increase (decrease) in goodwill						(66,600)		(94,800)
Business combination increase (decrease) in other current assets								121,700
Business combination increase (decrease) in accrued expenses and other current liabilities								(3,000)
Business combination increase (decrease) in income tax payable								$ 32,300
Estimated fair value of equity investments	[1]		1,460,440
Carryover of tax basis in goodwill, deductible for tax purposes			634,000
Carryover of tax basis in equity investments, deductible for tax purposes			360,000
Carryover of tax basis in property and equipment including assets held for sale, deductible for tax purposes			246,000
Noncontrolling interests	[1]		6,201
Revenue included in consolidated statements of operations and comprehensive income					$ 471,600
Operating income					$ 78,400
Merger related costs							$ 31,000		$ 38,300
Tribune [Member] | FCC Licenses [Member]
Business Acquisition [Line Items]
Carryover of tax basis in intangible assets, deductible for tax purposes			$ 60,000
Tribune [Member] | Minimum [Member]
Business Acquisition [Line Items]
Property and equipment, Estimated useful life			3 years
Tribune [Member] | Maximum [Member]
Business Acquisition [Line Items]
Property and equipment, Estimated useful life			39 years
Tribune [Member] | Network affiliation agreements [Member]
Business Acquisition [Line Items]
Business combination increase (decrease) in amortization of intangibles			$ 9,800
Network affiliation agreements useful life			15 years
Carryover of tax basis in intangible assets, deductible for tax purposes			$ 102,000
Tribune [Member] | Other definite-lived intangible assets [Member]
Business Acquisition [Line Items]
Weighted average estimated useful life of intangible assets			9 years
Carryover of tax basis in intangible assets, deductible for tax purposes			$ 288,000
Tribune [Member] | Senior Subordinated Notes [Member] | 5.625 % Due 2027 [Member]
Business Acquisition [Line Items]
Debt issuance			$ 1,120,000
Interest rate			5.625%
Tribune [Member] | Class A Common Stock [Member]
Business Acquisition [Line Items]
Common stock, par value | $ / shares			$ 0.001
Tribune [Member] | Class B Common Stock [Member]
Business Acquisition [Line Items]
Common stock, par value | $ / shares			$ 0.001
Tribune [Member] | TV Food Network [Member]
Business Acquisition [Line Items]
Business combination increase (decrease) in equity investment						$ (22,500)
Business combination increase (decrease) in amortization of basis difference			$ 16,000
Tribune [Member] | Tribune Divestitures [Member]
Business Acquisition [Line Items]
Number of stations divested | TelevisionStation			13
Number of television market of stations sold | Market			11
Selling price of entities sold			$ 1,008,000
Number of divested television stations sold | Station			13
Gain (Loss) on sale of business			$ 9,800
Tribune [Member] | Nexstar Divestitures
Business Acquisition [Line Items]
Selling price of entities sold			$ 358,600
Number of divested television stations sold | Station			8
Gain (Loss) on sale of business			$ 105,900
WDKY-TV [Member]
Business Acquisition [Line Items]
Acquisition date		Sep. 17, 2020
Bargain purchase gain		$ 19,000

[1] The purchase price allocation includes the effects of measurement period adjustments recorded in the fourth quarter of 2019 and in fiscal year 2020 as further discussed below.