Other matters - Narrative (Detail)			1 Months Ended			12 Months Ended			24 Months Ended	32 Months Ended
	Mar. 02, 2020 USD ($) market	Jul. 30, 2018 defendant	Jun. 30, 2019 defendant	Dec. 13, 2018 defendant	Apr. 30, 2017 USD ($) market	Dec. 31, 2020 USD ($) station customer	Dec. 31, 2019 USD ($) customer	Dec. 31, 2018 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Mar. 23, 2018 USD ($)
Commitments and Contingencies Disclosure [Line Items]
Proceeds from sale of minority ownership interest	$ 14,000,000.0					$ 14,000,000	$ 0	$ 0
Number of markets where stations were repacked | market					18
FCC Broadcast Spectrum Program, number of stations acquired | station						1
FCC Broadcast Spectrum Program, authorized reimbursement amount					$ 1,750,000,000
FCC Broadcast Spectrum Program, repacking fund											$ 1,000,000,000
FCC Broadcast Spectrum Program, repacking fund available for distributors											$ 750,000,000
FCC Broadcast Spectrum Program, capital expenditures incurred									$ 42,000,000.0
FCC Broadcast Spectrum Program, amount of reimbursement received										$ 37,600,000
FCC Broadcast Spectrum Program, remaining reimbursement expected to be received						$ 4,400,000
Gray Television [Member]
Commitments and Contingencies Disclosure [Line Items]
Number of television markets | market	93
Sales Revenue | Customer Concentration Risk
Commitments and Contingencies Disclosure [Line Items]
Number of customers which represent significant percentage of revenue | customer						1	2
Customer A | Sales Revenue | Customer Concentration Risk
Commitments and Contingencies Disclosure [Line Items]
Revenues						$ 393,400,000	$ 270,300,000	245,300,000
Customer B | Sales Revenue | Customer Concentration Risk
Commitments and Contingencies Disclosure [Line Items]
Revenues							251,200,000	$ 223,800,000
Settled Litigation
Commitments and Contingencies Disclosure [Line Items]
Number of defendants | defendant			4	7
Programming Contracts
Commitments and Contingencies Disclosure [Line Items]
Purchase commitments under contract						2,200,000,000
Equity And Debt Investment
Commitments and Contingencies Disclosure [Line Items]
Expenses incurred with related party						55,100,000	34,300,000
Accounts payable and accrued liabilities with related party						$ 13,500,000	$ 4,300,000		$ 13,500,000	$ 13,500,000
Clay, Massey & Associates, P.C. v. Gray Television
Commitments and Contingencies Disclosure [Line Items]
Number of defendants | defendant		16	4