CONDENSED CONSOLIDATED FINANCIAL STATEMENTS - Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Revenue	$ 734,002	$ 670,891	$ 679,290	$ 649,935	$ 797,691	$ 693,835	$ 666,534	$ 578,889	$ 2,734,118	$ 2,736,949	$ 2,219,136
Media production expenses									1,063,074	953,089	733,199
Selling, general and administrative									646,790	575,145	495,974
Depreciation, amortization and other operating expenses									286,748	605,862	567,227
Total operating expenses									1,996,612	2,134,096	1,796,400
Operating income	357,581	103,447	118,849	157,629	233,446	153,994	129,074	86,339	737,506	602,853	422,736
Equity in earnings of consolidated subsidiaries									0	0	0
Interest expense									(212,315)	(211,143)	(191,447)
Other income (expense)									(6,447)	(18,820)	2,504
Total other expense									(218,762)	(229,963)	(188,943)
Income tax benefit (provision)									75,360	(122,128)	(57,694)
NET INCOME									594,104	250,762	176,099
Net income attributable to the noncontrolling interests									(18,091)	(5,461)	(4,575)
Net income attributable to Sinclair Broadcast Group	$ 443,529	$ 30,637	$ 44,645	$ 57,202	$ 120,897	$ 50,845	$ 49,419	$ 24,140	576,013	245,301	171,524
Comprehensive income (loss)									593,488	250,789	181,720
Reportable legal entities | Sinclair Broadcast Group, Inc.
Condensed Financial Statements, Captions [Line Items]
Revenue									0	0	0
Media production expenses									0	0	0
Selling, general and administrative									9,204	4,062	4,441
Depreciation, amortization and other operating expenses									984	1,064	1,065
Total operating expenses									10,188	5,126	5,506
Operating income									(10,188)	(5,126)	(5,506)
Equity in earnings of consolidated subsidiaries									579,954	244,580	170,104
Interest expense									(88)	(238)	(382)
Other income (expense)									1,678	3,613	4,765
Total other expense									581,544	247,955	174,487
Income tax benefit (provision)									4,657	2,472	2,543
NET INCOME									576,013	245,301	171,524
Net income attributable to the noncontrolling interests									0	0	0
Net income attributable to Sinclair Broadcast Group									576,013	245,301	171,524
Comprehensive income (loss)									593,488	250,789	181,720
Reportable legal entities | Sinclair Television Group, Inc.
Condensed Financial Statements, Captions [Line Items]
Revenue									0	0	0
Media production expenses									0	0	0
Selling, general and administrative									102,930	70,503	58,543
Depreciation, amortization and other operating expenses									6,250	7,331	3,779
Total operating expenses									109,180	77,834	62,322
Operating income									(109,180)	(77,834)	(62,322)
Equity in earnings of consolidated subsidiaries									793,620	463,598	343,183
Interest expense									(205,107)	(198,893)	(180,166)
Other income (expense)									5,077	(22,867)	(151)
Total other expense									593,590	241,838	162,866
Income tax benefit (provision)									100,473	99,148	81,626
NET INCOME									584,883	263,152	182,170
Net income attributable to the noncontrolling interests									0	0	0
Net income attributable to Sinclair Broadcast Group									584,883	263,152	182,170
Comprehensive income (loss)									584,267	263,179	187,791
Reportable legal entities | Guarantor Subsidiaries and KDSM, LLC
Condensed Financial Statements, Captions [Line Items]
Revenue									2,593,623	2,579,284	2,076,851
Media production expenses									1,011,965	918,200	725,037
Selling, general and administrative									522,039	489,882	418,885
Depreciation, amortization and other operating expenses									219,390	465,680	433,690
Total operating expenses									1,753,394	1,873,762	1,577,612
Operating income									840,229	705,522	499,239
Equity in earnings of consolidated subsidiaries									(16)	220	195
Interest expense									(4,586)	(4,481)	(4,658)
Other income (expense)									(5,790)	715	269
Total other expense									(10,392)	(3,546)	(4,194)
Income tax benefit (provision)									(30,171)	(231,504)	(146,331)
NET INCOME									799,666	470,472	348,714
Net income attributable to the noncontrolling interests									0	0	0
Net income attributable to Sinclair Broadcast Group									799,666	470,472	348,714
Comprehensive income (loss)									799,666	470,472	351,760
Reportable legal entities | Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Revenue									221,377	265,855	221,633
Media production expenses									124,044	135,511	82,450
Selling, general and administrative									14,800	10,804	14,272
Depreciation, amortization and other operating expenses									62,924	133,810	131,373
Total operating expenses									201,768	280,125	228,095
Operating income									19,609	(14,270)	(6,462)
Equity in earnings of consolidated subsidiaries									0	0	0
Interest expense									(21,643)	(32,521)	(30,022)
Other income (expense)									(7,412)	(281)	(2,379)
Total other expense									(29,055)	(32,802)	(32,401)
Income tax benefit (provision)									401	7,756	4,468
NET INCOME									(9,045)	(39,316)	(34,395)
Net income attributable to the noncontrolling interests									(17,738)	(4,937)	(4,914)
Net income attributable to Sinclair Broadcast Group									(26,783)	(44,253)	(39,309)
Comprehensive income (loss)									(9,045)	(39,316)	(39,309)
Eliminations
Condensed Financial Statements, Captions [Line Items]
Revenue									(80,882)	(108,190)	(79,348)
Media production expenses									(72,935)	(100,622)	(74,288)
Selling, general and administrative									(2,183)	(106)	(167)
Depreciation, amortization and other operating expenses									(2,800)	(2,023)	(2,680)
Total operating expenses									(77,918)	(102,751)	(77,135)
Operating income									(2,964)	(5,439)	(2,213)
Equity in earnings of consolidated subsidiaries									(1,373,558)	(708,398)	(513,482)
Interest expense									19,109	24,990	23,781
Other income (expense)									0	0	0
Total other expense									(1,354,449)	(683,408)	(489,701)
Income tax benefit (provision)									0	0	0
NET INCOME									(1,357,413)	(688,847)	(491,914)
Net income attributable to the noncontrolling interests									(353)	(524)	339
Net income attributable to Sinclair Broadcast Group									(1,357,766)	(689,371)	(491,575)
Comprehensive income (loss)									$ (1,374,888)	$ (694,335)	$ (500,242)