Goodwill and other intangible assets - Intangible Assets and Goodwill (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 2,981,587	$ 2,968,693
Accumulated Amortization	0	0
Finite-Lived Intangible Assets [Line Items]
Accumulated Amortization	(267,115)	(235,582)
Total indefinite-lived and amortizable intangible assets	2,740,081	2,739,226
Television and radio station FCC broadcast licenses
Indefinite-lived Intangible Assets [Line Items]
Television and radio station FCC broadcast licenses	2,123,898	2,123,898
Retransmission agreements
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets:	235,215	235,215
Accumulated Amortization	(153,684)	(138,928)
Network affiliation agreements
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets:	309,503	309,503
Accumulated Amortization	(84,945)	(72,694)
Other
Finite-Lived Intangible Assets [Line Items]
Amortizable intangible assets:	71,465	70,610
Accumulated Amortization	$ (28,486)	$ (23,960)