Goodwill and other intangible assets - Goodwill, Indefinite-Lived Intangible Assets, and Amortizable Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Line Items]
Goodwill, gross	$ 2,596,863	$ 2,579,417
Goodwill, accumulated amortization	0	0
Goodwill	2,596,863	2,579,417
Amortizable intangible assets:
Amortizable intangible assets, net	141,891
Total intangible assets, gross	4,241,898	3,940,806
Intangible assets, accumulated amortization	(118,958)	(88,120)
Total intangible assets, net	4,122,940	3,852,686
Retransmission agreements
Amortizable intangible assets:
Amortizable intangible assets, gross	121,594	110,191
Amortizable intangible assets, accumulated amortization	(79,274)	(62,355)
Amortizable intangible assets, net	42,320	47,836
Network affiliation agreements
Amortizable intangible assets:
Amortizable intangible assets, gross	110,390	43,485
Amortizable intangible assets, accumulated amortization	(30,802)	(19,371)
Amortizable intangible assets, net	79,588	24,114
Other
Amortizable intangible assets:
Amortizable intangible assets, gross	28,865	15,763
Amortizable intangible assets, accumulated amortization	(8,882)	(6,394)
Amortizable intangible assets, net	19,983	9,369
Television station FCC licenses
Indefinite-lived intangibles:
Television station FCC licenses	$ 1,384,186	$ 1,191,950