Business Segment Information - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($) market station	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) market station	Sep. 30, 2016 USD ($)
Segment Reporting Information [Line Items]
Operating income	$ 116,861	$ 185,851	$ 390,052	$ 497,889
Accounting Standards Update 2017-06 | Effect of Accounting Change | Operating Segments
Segment Reporting Information [Line Items]
Operating income	$ 1,700	1,800	$ 4,900	5,800
Media
Segment Reporting Information [Line Items]
Number of television stations | station	46		46
Number of markets In which entity operates | market	38		38
Media | Operating Segments
Segment Reporting Information [Line Items]
Operating income	$ 130,338	$ 219,766	$ 433,629	$ 568,163