CONDENSED CONSOLIDATED FINANCIAL STATEMENTS - Statement of Cash Flows (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES		$ 647,418	$ 431,413	[1]	$ 611,590	[1]
CASH FLOWS (USED IN) FROM INVESTING ACTIVITIES:
Acquisition of property and equipment		(105,061)	(83,812)	[1]	(94,465)	[1]
Acquisition of businesses, net of cash acquired		0	(271,273)	[1]	(425,657)	[1]
Purchase of alarm monitoring contracts		0	(5,682)	[1]	(40,206)	[1]
Proceeds from the sale of assets		1,616	195,209	[1]	17,202	[1]
Investments in equity investees		(35,805)	(55,129)	[1]	(51,247)	[1]
Distributions from equity method investees		22,834	12,178	[1]	6,786	[1]
Spectrum auction proceeds		0	310,802	[1]	0	[1]
Other, net		(1,795)	12,291		(15,155)
Net cash flows (used in) from investing activities		(118,211)	114,584	[1]	(609,528)	[1]
CASH FLOWS (USED IN) FROM FINANCING ACTIVITIES:
Proceeds from notes payable, commercial bank financing and capital leases		4,317	166,797	[1]	1,024,912	[1]
Repayments of notes payable, commercial bank financing and capital leases		(166,785)	(340,108)	[1]	(674,439)	[1]
Proceeds from the sale of Class A Common Stock		0	487,883	[1]	0	[1]
Dividends paid on Class A and Class B Common Stock		(74,566)	(71,364)	[1]	(65,909)	[1]
Repurchase of outstanding Class A Common Stock		(220,889)	(30,287)	[1]	(136,283)	[1]
Payments for deferred financing costs		(922)	(731)	[1]	(35,505)	[1]
Distributions to noncontrolling interests		(8,901)	(22,416)	[1]	(10,464)	[1]
Increase (decrease) in intercompany payables		0	0		0
Other, net		2,929	(15)		2,113
Net cash flows (used in) from financing activities		(464,817)	189,759	[1]	104,425	[1]
NET INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH		64,390	735,756	[1]	106,487	[1]
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, beginning of year	[1]	995,940	260,184		153,697
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, end of year		1,060,330	995,940	[1]	260,184	[1]
Reportable legal entities | Sinclair Broadcast Group, Inc.
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES		(8,542)	(8,659)		(11,784)
CASH FLOWS (USED IN) FROM INVESTING ACTIVITIES:
Acquisition of property and equipment		(1)	(130)		0
Acquisition of businesses, net of cash acquired			0		0
Purchase of alarm monitoring contracts			0		0
Proceeds from the sale of assets		0	0		0
Investments in equity investees		(2,587)	(946)		(2,945)
Distributions from equity method investees		4,728	5,857
Spectrum auction proceeds			0
Other, net		1,670	740		1,714
Net cash flows (used in) from investing activities		3,810	5,521		(1,231)
CASH FLOWS (USED IN) FROM FINANCING ACTIVITIES:
Proceeds from notes payable, commercial bank financing and capital leases		0	0		0
Repayments of notes payable, commercial bank financing and capital leases		0	(1,858)		(1,651)
Proceeds from the sale of Class A Common Stock			487,883
Dividends paid on Class A and Class B Common Stock		(74,566)	(71,364)		(65,909)
Repurchase of outstanding Class A Common Stock		(220,889)	(30,287)		(136,283)
Payments for deferred financing costs		0	0		0
Distributions to noncontrolling interests		0	0		0
Increase (decrease) in intercompany payables		297,256	(381,344)		218,054
Other, net		2,931	108		(1,196)
Net cash flows (used in) from financing activities		4,732	3,138		13,015
NET INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH		0	0		0
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, beginning of year		0	0		0
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, end of year		0	0		0
Reportable legal entities | Sinclair Television Group, Inc.
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES		(252,615)	(180,966)		(130,406)
CASH FLOWS (USED IN) FROM INVESTING ACTIVITIES:
Acquisition of property and equipment		(6,592)	(14,973)		(8,006)
Acquisition of businesses, net of cash acquired			(8,308)		0
Purchase of alarm monitoring contracts			0		0
Proceeds from the sale of assets		0	0		0
Investments in equity investees		(1,975)	(720)		(15,620)
Distributions from equity method investees		0	0
Spectrum auction proceeds			0
Other, net		(12,091)	11,551		(25,120)
Net cash flows (used in) from investing activities		(20,658)	(12,450)		(48,746)
CASH FLOWS (USED IN) FROM FINANCING ACTIVITIES:
Proceeds from notes payable, commercial bank financing and capital leases		0	159,669		995,000
Repayments of notes payable, commercial bank financing and capital leases		(148,505)	(213,919)		(650,422)
Proceeds from the sale of Class A Common Stock			0
Dividends paid on Class A and Class B Common Stock		0	0		0
Repurchase of outstanding Class A Common Stock		0	0		0
Payments for deferred financing costs		0	(425)		(35,254)
Distributions to noncontrolling interests		0	0		0
Increase (decrease) in intercompany payables		737,911	660,911		(17,778)
Other, net		0	713		407
Net cash flows (used in) from financing activities		589,406	606,949		291,953
NET INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH		316,133	413,533		112,801
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, beginning of year		645,830	232,297		119,496
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, end of year		961,963	645,830		232,297
Reportable legal entities | Guarantor Subsidiaries and KDSM, LLC
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES		936,385	600,070		721,991
CASH FLOWS (USED IN) FROM INVESTING ACTIVITIES:
Acquisition of property and equipment		(98,201)	(68,475)		(82,450)
Acquisition of businesses, net of cash acquired			(262,965)		(415,282)
Purchase of alarm monitoring contracts			0		0
Proceeds from the sale of assets		1,616	568		8,069
Investments in equity investees		(27,960)	(20,701)		(27)
Distributions from equity method investees		0	0
Spectrum auction proceeds			310,802
Other, net		8,626	0		3,179
Net cash flows (used in) from investing activities		(115,919)	(40,771)		(486,511)
CASH FLOWS (USED IN) FROM FINANCING ACTIVITIES:
Proceeds from notes payable, commercial bank financing and capital leases		0	0		0
Repayments of notes payable, commercial bank financing and capital leases		(3,554)	(3,381)		(3,007)
Proceeds from the sale of Class A Common Stock			0
Dividends paid on Class A and Class B Common Stock		0	0		0
Repurchase of outstanding Class A Common Stock		0	0		0
Payments for deferred financing costs		0	0		0
Distributions to noncontrolling interests		0	0		0
Increase (decrease) in intercompany payables		(1,117,417)	(242,402)		(224,551)
Other, net		(3,230)	(1,008)		2,718
Net cash flows (used in) from financing activities		(1,124,201)	(246,791)		(224,840)
NET INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH		(303,735)	312,508		10,640
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, beginning of year		323,383	10,875		235
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, end of year		19,648	323,383		10,875
Reportable legal entities | Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES		(40,533)	12,424		7,914
CASH FLOWS (USED IN) FROM INVESTING ACTIVITIES:
Acquisition of property and equipment		(3,914)	(2,930)		(5,009)
Acquisition of businesses, net of cash acquired			0		(10,375)
Purchase of alarm monitoring contracts			(5,682)		(40,206)
Proceeds from the sale of assets		0	194,641		9,133
Investments in equity investees		(3,283)	(32,762)		(32,655)
Distributions from equity method investees		18,106	6,321
Spectrum auction proceeds			0
Other, net		0	0		5,072
Net cash flows (used in) from investing activities		10,909	159,588		(74,040)
CASH FLOWS (USED IN) FROM FINANCING ACTIVITIES:
Proceeds from notes payable, commercial bank financing and capital leases		4,317	7,128		29,912
Repayments of notes payable, commercial bank financing and capital leases		(15,120)	(121,270)		(19,612)
Proceeds from the sale of Class A Common Stock			0
Dividends paid on Class A and Class B Common Stock		0	0		0
Repurchase of outstanding Class A Common Stock		0	0		0
Payments for deferred financing costs		(922)	(306)		(251)
Distributions to noncontrolling interests		(8,901)	(22,416)		(10,464)
Increase (decrease) in intercompany payables		100,440	(25,605)		49,403
Other, net		1,802	172		184
Net cash flows (used in) from financing activities		81,616	(162,297)		49,172
NET INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH		51,992	9,715		(16,954)
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, beginning of year		26,727	17,012		33,966
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, end of year		78,719	26,727		17,012
Eliminations
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES		12,723	8,544		23,875
CASH FLOWS (USED IN) FROM INVESTING ACTIVITIES:
Acquisition of property and equipment		3,647	2,696		1,000
Acquisition of businesses, net of cash acquired			0		0
Purchase of alarm monitoring contracts			0		0
Proceeds from the sale of assets		0	0		0
Investments in equity investees		0	0		0
Distributions from equity method investees		0	0
Spectrum auction proceeds			0
Other, net		0	0		0
Net cash flows (used in) from investing activities		3,647	2,696		1,000
CASH FLOWS (USED IN) FROM FINANCING ACTIVITIES:
Proceeds from notes payable, commercial bank financing and capital leases		0	0		0
Repayments of notes payable, commercial bank financing and capital leases		394	320		253
Proceeds from the sale of Class A Common Stock			0
Dividends paid on Class A and Class B Common Stock		0	0		0
Repurchase of outstanding Class A Common Stock		0	0		0
Payments for deferred financing costs		0	0		0
Distributions to noncontrolling interests		0	0		0
Increase (decrease) in intercompany payables		(18,190)	(11,560)		(25,128)
Other, net		1,426	0		0
Net cash flows (used in) from financing activities		(16,370)	(11,240)		(24,875)
NET INCREASE IN CASH, CASH EQUIVALENTS, AND RESTRICTED CASH		0	0		0
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, beginning of year		0	0		0
CASH, CASH EQUIVALENTS, AND RESTRICTED CASH, end of year		$ 0	$ 0		$ 0

[1] See Recent Accounting Pronouncements within Note 1. Nature of Operations and Summary of Significant Accounting Policies for a discussion of the adoption of new accounting principles related to the classification of certain cash receipts and cash payments.