QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Total revenues, net	$ 893,325	$ 766,261	$ 730,143	$ 665,352	$ 712,512	$ 644,532	$ 652,235	$ 626,936	$ 3,055,081	$ 2,636,215	$ 2,622,510
Operating income	262,954	157,810	131,583	107,314	357,581	103,447	118,849	157,629	659,661	737,506	602,853
Net income	207,694	65,000	29,310	43,994	444,800	32,566	46,035	70,703	345,998	594,104	250,762
Net income attributable to Sinclair Broadcast Group	$ 206,201	$ 63,875	$ 28,042	$ 43,123	$ 443,529	$ 30,637	$ 44,645	$ 57,202	$ 341,241	$ 576,013	$ 245,301
Basic earnings per share common shares (in dollars per share)	$ 2.12	$ 0.63	$ 0.27	$ 0.42	$ 4.36	$ 0.30	$ 0.43	$ 0.62	$ 3.38	$ 5.77	$ 2.62
Diluted earnings per share common shares (in dollars per share)	$ 2.10	$ 0.62	$ 0.27	$ 0.42	$ 4.32	$ 0.30	$ 0.43	$ 0.61	$ 3.35	$ 5.72	$ 2.60
Gain (loss) recognized on sale					$ 225,300				$ 5,800
Federal tax reform					$ 272,100				$ 4,300	$ 272,100