Goodwill and Other Intangible Assets - Summary of other intangible assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Carrying amount:
Total carrying amount	$ 455,841	$ 437,337
Accumulated amortization:
Total accumulated amortization	(124,416)	(115,599)
Net amortizable intangible assets	331,425	321,738
Total other intangible assets	495,440	478,953
Indefinite-lived intangible assets - FCC licenses
Accumulated amortization:
Indefinite-lived intangible assets — FCC licenses	164,015	157,215
Television network affiliation relationships
Carrying amount:
Total carrying amount	265,844	248,444
Accumulated amortization:
Total accumulated amortization	(65,333)	(62,020)
Customer lists and advertiser relationships
Carrying amount:
Total carrying amount	101,200	100,500
Accumulated amortization:
Total accumulated amortization	(39,216)	(36,380)
Other
Carrying amount:
Total carrying amount	88,797	88,393
Accumulated amortization:
Total accumulated amortization	$ (19,867)	$ (17,199)