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Loss contingency, settlement agreement, amount.

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Net cash received from legal settlements.

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Number of proofs of claim against debtors.

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Number of proofs of claim against debtors withdrawn.

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Percentage of membership interest sold.

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The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees.

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

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The amount of estimated penalties recognized in the period arising from income tax examinations.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to state and local income tax expense (benefit).

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Date the pending litigation matter was dismissed, in CCYY-MM-DD format.

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States the date the complaint was formally filed in a court of law, in arbitration or mediation.

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Name of the other party to the settlement agreement.

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The effective date of a duly executed litigation settlement agreement.

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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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Amount of cash outflow for taxes classified as other.

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Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of unrecognized tax benefits.

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Commitments and Contingencies - Additional Information (Details) $ in Thousands									1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 02, 2020 USD ($)	Jul. 15, 2020 USD ($)	Jan. 28, 2020 USD ($)	Jan. 27, 2020 USD ($)	Sep. 19, 2019 USD ($)	Jan. 22, 2019 USD ($)	Jun. 28, 2016 USD ($)	Dec. 31, 2012 Proof	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Proof	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Aug. 21, 2009
Loss Contingency, Information about Litigation Matters [Abstract]
Restricted cash and cash equivalents									$ 16,610	$ 16,610		$ 16,610		$ 16,608
Payment for non-license assets				$ 18,000
Cash payment			$ 98,000
Income tax expense (benefit)										65,177	$ 39,507	166,927	$ 82,594
Increase in deferred income tax liability												20,940	$ 14,899
Chicago Cubs Transactions [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Estimated federal and state income taxes						$ 225,000
Tax payments						$ 147,000
Chicago Cubs Transactions [Member] \| Internal Revenue Service ("IRS") [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Income tax expense (benefit)							$ 182,000
Income tax penalties expense							$ 73,000		115,000
Chicago Cubs Transactions [Member] \| Northside Entertainment Holdings LLC [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Ownership interest percentage															95.00%
Chicago Cubs Transactions [Member] \| Chicago Entertainment Ventures, LLC [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Ownership interest percentage															5.00%
Tribune [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Number of proofs of claim filed against debtors \| Proof								7,400
Restricted cash and cash equivalents									16,600	16,600		$ 16,600
Number of proofs of claim against debtors withdrawn \| Proof												296
Cash payment					$ 4,197,198
Tribune [Member] \| Internal Revenue Service ("IRS") [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Increase in federal and state taxes payable										40,000
Increase in deferred income tax liability										140,000
Unrecognized tax benefits									11,000	11,000		$ 11,000
Tribune [Member] \| Chicago Cubs Transactions [Member] \| Chicago Entertainment Ventures, LLC [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Percentage of membership interest sold						5.00%
Assets of WDKY-TV [Member] \| Sinclair Broadcast Group, Inc. [Member] \| Lexington, KY [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Cash payment		$ 18,000
Multi District Litigation [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Loss contingency lawsuit filing date												April 3, 2019
Loss contingency dismissal date												Sep. 05, 2019
Multi District Litigation [Member] \| Second Amended Complaint [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Loss contingency lawsuit filing date												September 9, 2019
Loss contingency dismissal date												Oct. 08, 2019
Marshall Litigation [Member] \| Subsequent Event [Member]
Loss Contingency, Information about Litigation Matters [Abstract]
Loss contingency, settlement agreement, date	November 2, 2020
Loss contingency, settlement agreement, terms	As of the filing of this Quarterly Report on Form 10-Q, Marshall has not received the required approval. If the Bankruptcy Court of the Southern District of Texas does not approve, the settlement between Nexstar and Marshall is terminated and void and Nexstar is not required to pay the cash consideration to Marshall, and the litigation will recommence.
Loss contingency, settlement agreement, counterparty's name	Marshall
Loss contingency, settlement agreement amount	$ 2,250
Nexstar [Member] \| Financial Guarantee of Mission Debt [Member]
Guarantees of Mission, Marshall and Shield Debt [Abstract]
Maximum commitment under credit agreement									250,000	250,000		$ 250,000
Commitment under credit agreement at carrying value									225,000	225,000		$ 225,000
Line of credit facility maturity period												2023-10
Nexstar [Member] \| Financial Guarantee Shield Debt [Member]
Guarantees of Mission, Marshall and Shield Debt [Abstract]
Commitment under credit agreement at carrying value									$ 21,000	$ 21,000		$ 21,000
Line of credit facility maturity period												2023-10