Accounting policies - Narrative (Details) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended
	Feb. 22, 2022 USD ($) $ / shares	Mar. 31, 2020	Mar. 31, 2022 USD ($) segment station radioStation market $ / shares	Dec. 31, 2021 USD ($) $ / shares
Disaggregation of Revenue [Line Items]
Number of operating segments | segment			1
Number of reportable segments | segment			1
Number of television stations | station			64
Number of radio stations | radioStation			2
Number of markets in which entity operates | market			51
Common stock, par value (in dollars per share)	$ 1.00		$ 1	$ 1
Allowance for doubtful accounts receivable | $			$ 4,810	$ 4,371
Commercial reselling agreement, term		3 years
Business Combination Termination Scenario One | Teton Parent Corp
Disaggregation of Revenue [Line Items]
Termination fee | $	$ 136,000
Business Combination Termination Scenario Two | Teton Parent Corp
Disaggregation of Revenue [Line Items]
Termination fee | $	$ 272,000
Teton Parent Corp
Disaggregation of Revenue [Line Items]
Conversion price (in dollars per share)	$ 24.00
Termination fee | $	$ 163,000
Teton Parent Corp | Closing between 9- and 12-month anniversary of signing
Disaggregation of Revenue [Line Items]
Ticking fee, per day (dollars per share)	$ 0.00167
Ticking fee, per month (dollars per share)	0.05
Teton Parent Corp | Closing between 12- and 13-month anniversary of signing
Disaggregation of Revenue [Line Items]
Ticking fee, per day (dollars per share)	0.0025
Ticking fee, per month (dollars per share)	0.075
Teton Parent Corp | Closing between 13- and 14-month anniversary of signing
Disaggregation of Revenue [Line Items]
Ticking fee, per day (dollars per share)	0.00333
Ticking fee, per month (dollars per share)	0.10
Teton Parent Corp | Closing after 14-month anniversary of signing
Disaggregation of Revenue [Line Items]
Ticking fee, per day (dollars per share)	0.00417
Ticking fee, per month (dollars per share)	$ 0.125