Goodwill and Other Intangible Assets - Summary of other intangible assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Carrying amount:
Total carrying amount	$ 437,337	$ 355,013
Accumulated amortization:
Total accumulated amortization	(115,599)	(86,253)
Net amortizable intangible assets	321,738	268,760
Total other intangible assets	478,953	425,975
FCC licenses
Accumulated amortization:
Other indefinite-lived intangible assets - FCC licenses	157,215	157,215
Television network affiliation relationships
Carrying amount:
Total carrying amount	248,444	248,444
Accumulated amortization:
Total accumulated amortization	(62,020)	(49,639)
Customer lists and advertiser relationships
Carrying amount:
Total carrying amount	100,500	69,500
Accumulated amortization:
Total accumulated amortization	(36,380)	(26,345)
Other intangible assets
Carrying amount:
Total carrying amount	88,393	37,069
Accumulated amortization:
Total accumulated amortization	$ (17,199)	$ (10,269)