Goodwill and other intangible assets - Intangible Assets and Goodwill (Details) $ in Thousands	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) station
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill, gross	$ 2,967,383	$ 2,950,587
Total indefinite-live and amortizable intangible assets	2,723,356	2,730,066
Goodwill, accumulated amortization	0	0
Total indefinite-live and amortizable intangible assets, accumulated amortization	(184,669)	$ (168,452)
Number of stations acquired | station		15
Retransmission agreements
Goodwill and Intangible Assets Disclosure [Line Items]
Amortizable intangible assets, gross	235,215	$ 256,533
Amortizable intangible assets, accumulated amortization	(112,853)	(105,212)
Network affiliation agreements
Goodwill and Intangible Assets Disclosure [Line Items]
Amortizable intangible assets, gross	309,503	309,496
Amortizable intangible assets, accumulated amortization	(54,319)	(48,174)
Other
Goodwill and Intangible Assets Disclosure [Line Items]
Amortizable intangible assets, gross	73,306	73,305
Amortizable intangible assets, accumulated amortization	(17,497)	(15,066)
Television and radio station FCC broadcast licenses
Goodwill and Intangible Assets Disclosure [Line Items]
Indefinite-lived intangibles, gross	$ 2,105,332	$ 2,090,732