Other matters (Details) $ in Millions		1 Months Ended		3 Months Ended		6 Months Ended
	Jul. 30, 2018 defendant	Jun. 30, 2019 defendant	Dec. 13, 2018 defendant	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Business Acquisition [Line Items]
FCC reimbursements received				$ 3.0
Remaining FFC reimbursements expected to be received				1.6
Settled litigation
Business Acquisition [Line Items]
Number of other broadcasters settling DOJ complaint (defendant) | defendant		4	7
Equity And Debt Investment | Affiliated Entity
Business Acquisition [Line Items]
Expenses incurred with related party				18.5	$ 13.7	$ 42.4	$ 24.2
Accounts payable and accrued liabilities with related party				$ 7.0		$ 7.0		$ 13.5
Clay, Massey & Associates, P.C. v. Gray Television
Business Acquisition [Line Items]
Number of other broadcasters settling DOJ complaint (defendant) | defendant	16	4