Goodwill and other intangible assets - Intangible Assets and Goodwill (Details) $ in Thousands	3 Months Ended
	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) station
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill, gross	$ 2,968,655	$ 2,950,587
Total indefinite-live and amortizable intangible assets	2,719,495	2,730,066
Goodwill, accumulated amortization	0	0
Total indefinite-live and amortizable intangible assets, accumulated amortization	(201,355)	$ (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	(121,544)	(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	(60,444)	(48,174)
Other
Goodwill and Intangible Assets Disclosure [Line Items]
Amortizable intangible assets, gross	70,610	73,305
Amortizable intangible assets, accumulated amortization	(19,367)	(15,066)
Television and radio station FCC broadcast licenses
Goodwill and Intangible Assets Disclosure [Line Items]
Indefinite-lived intangibles, gross	2,104,167	$ 2,090,732
Brand name
Goodwill and Intangible Assets Disclosure [Line Items]
Impairment of brand name	$ 2,100