Acquisitions and Dispositions - Reiten - Additional Information (Details) $ in Thousands			3 Months Ended								11 Months Ended	12 Months Ended
	Feb. 01, 2016 USD ($) TelevisionStation	Sep. 30, 2015 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Revenue included in consolidated statements of operations and comprehensive income			$ 653,664	$ 611,870	$ 626,115	$ 540,317	$ 309,879	$ 275,659	$ 261,994	$ 255,658		$ 2,431,966	$ 1,103,190	$ 896,377
Operating income (loss)			$ 140,837	$ 129,072	$ 138,685	$ 110,151	$ 92,475	$ 72,897	$ 64,007	$ 57,929		$ 518,745	$ 287,308	$ 206,107
Network Affiliation Agreements [Member]
Business Acquisition [Line Items]
Network affiliation agreements useful life												15 years	15 years	15 years
Reiten [Member]
Business Acquisition [Line Items]
Acquisition date	Feb. 01, 2016
Number of television stations acquired | TelevisionStation	4
Purchase price of entities acquired	$ 44,000
Deposit paid upon signing an agreement to acquire a business		$ 2,200
Acquisition related costs													$ 100
Revenue included in consolidated statements of operations and comprehensive income											$ 11,100
Operating income (loss)											$ 1,000
Reiten [Member] | Network Affiliation Agreements [Member]
Business Acquisition [Line Items]
Network affiliation agreements useful life	15 years
Reiten [Member] | Other definite-lived intangible assets [Member]
Business Acquisition [Line Items]
Weighted average estimated useful life of other intangible assets	2 years 6 months