Other matters - Narrative (Detail)			1 Months Ended			3 Months Ended	12 Months Ended
	Jun. 17, 2019 defendant	Jul. 30, 2018 defendant	Jun. 30, 2019 defendant	Dec. 13, 2018 defendant	Apr. 30, 2017 USD ($) station phase	Sep. 30, 2018 USD ($)	Dec. 31, 2019 USD ($) customer	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 23, 2018 USD ($)
Commitments and Contingencies Disclosure [Line Items]
FCC Broadcast Spectrum Program, number of stations affected | station					17
FCC Broadcast Spectrum Program, number of stations acquired | station					4
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, repacking period					39 months
FCC Broadcast Spectrum Program, number of repacking phases | phase					10
FCC Broadcast Spectrum Program, phase two | phase					2
FCC Broadcast Spectrum Program, phase nine | phase					9
FCC Broadcast Spectrum Program, capital expenditures incurred							$ 35,600,000
FCC Broadcast Spectrum Program, amount purchased							18,000,000.0
FCC Broadcast Spectrum Program, amount of reimbursement received							$ 24,400,000
FCC Broadcast Spectrum Program, amounts reimbursed as a percentage of total costs					92.50%
Severance charge						$ 7,300,000
Sales Revenue | Customer Concentration Risk
Commitments and Contingencies Disclosure [Line Items]
Number of customers which represent significant percentage of revenue | customer							2
Customer A | Sales Revenue | Customer Concentration Risk
Commitments and Contingencies Disclosure [Line Items]
Revenues							$ 270,300,000	$ 245,300,000	$ 215,400,000
Customer B | Sales Revenue | Customer Concentration Risk
Commitments and Contingencies Disclosure [Line Items]
Revenues							251,200,000	223,800,000	$ 202,400,000
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							2,310,000,000
Purchase Obligations
Commitments and Contingencies Disclosure [Line Items]
Purchase commitments under contract							129,500,000
Purchase Obligations
Commitments and Contingencies Disclosure [Line Items]
Purchase obligations							129,530,000
Equity And Debt Investment
Commitments and Contingencies Disclosure [Line Items]
Expenses incurred with related party							34,300,000	3,400,000
Accounts payable and accrued liabilities with related party							$ 4,300,000	$ 1,600,000
Clay, Massey & Associates, P.C. v. Gray Television
Commitments and Contingencies Disclosure [Line Items]
Number of defendants | defendant		16	4