CONDENSED CONSOLIDATED FINANCIAL STATEMENTS - Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES	$ 431,104	$ 591,766	$ 402,927
CASH FLOWS USED IN INVESTING ACTIVITIES:
Acquisition of property and equipment	(83,812)	(94,465)	(91,421)
Acquisition of businesses, net of cash acquired	(271,273)	(425,857)	(17,011)
Purchase of alarm monitoring contracts	(5,682)	(40,206)	(39,185)
Proceeds from the sale of assets	192,634	16,396	23,650
Investments in equity and cost method investees	(55,129)	(51,247)	(44,715)
Other, net	25,237	(10,624)	17,371
Net cash flow used in investing activities	(198,025)	(606,003)	(151,311)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Proceeds from notes payable, commercial bank financing and capital leases	166,797	1,024,912	382,887
Repayments of notes payable, commercial bank financing and capital leases	(336,501)	(671,215)	(395,147)
Proceeds from the sale of Class A Common Stock	487,883	0	0
Dividends paid on Class A and Class B Common Stock	(71,364)	(65,909)	(62,733)
Repurchase of outstanding Class A Common Stock	(30,287)	(136,283)	(28,823)
Payments for deferred financing costs	(731)	(15,681)	(3,847)
Noncontrolling interests distributions	(22,416)	(10,464)	(9,918)
Increase (decrease) in intercompany payables	0	0	0
Other, net	(5,849)	(1,111)	(1,745)
Net cash flows from (used in) financing activities	188,263	124,249	(119,326)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	421,342	110,012	132,290
CASH AND CASH EQUIVALENTS, beginning of year	259,984	149,972	17,682
CASH AND CASH EQUIVALENTS, end of year	681,326	259,984	149,972
Reportable legal entities | Sinclair Broadcast Group, Inc.
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES	(8,659)	(11,784)	(3,759)
CASH FLOWS USED IN INVESTING ACTIVITIES:
Acquisition of property and equipment	(130)	0	0
Acquisition of businesses, net of cash acquired	0	0	0
Purchase of alarm monitoring contracts	0	0	0
Proceeds from the sale of assets	0	0	0
Investments in equity and cost method investees	(946)	(2,945)	0
Other, net	6,597	1,714	4,598
Net cash flow used in investing activities	5,521	(1,231)	4,598
CASH FLOWS FROM (USED IN) 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	0	(528)
Proceeds from the sale of Class A Common Stock	487,883
Dividends paid on Class A and Class B Common Stock	(71,364)	(65,909)	(62,733)
Repurchase of outstanding Class A Common Stock	(30,287)	(136,283)	(28,823)
Payments for deferred financing costs		0	0
Noncontrolling interests distributions	0	0	0
Increase (decrease) in intercompany payables	(381,344)	218,054	89,319
Other, net	(1,750)	(2,847)	1,926
Net cash flows from (used in) financing activities	3,138	13,015	(839)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	0	0	0
CASH AND CASH EQUIVALENTS, beginning of year	0	0
CASH AND CASH EQUIVALENTS, 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	(180,966)	(150,230)	(131,363)
CASH FLOWS USED IN INVESTING ACTIVITIES:
Acquisition of property and equipment	(14,973)	(8,006)	(6,605)
Acquisition of businesses, net of cash acquired	(8,308)	0	0
Purchase of alarm monitoring contracts	0	0	0
Proceeds from the sale of assets	0	0	0
Investments in equity and cost method investees	(720)	(15,620)	(8,998)
Other, net	11,551	(21,395)	(5,447)
Net cash flow used in investing activities	(12,450)	(45,021)	(21,050)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Proceeds from notes payable, commercial bank financing and capital leases	159,669	995,000	349,562
Repayments of notes payable, commercial bank financing and capital leases	(213,919)	(650,422)	(382,691)
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		(15,430)	(3,604)
Noncontrolling interests distributions	0	0	0
Increase (decrease) in intercompany payables	660,911	(17,778)	303,755
Other, net	288	407	(2,232)
Net cash flows from (used in) financing activities	606,949	311,777	264,790
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	413,533	116,526	112,377
CASH AND CASH EQUIVALENTS, beginning of year	232,297	115,771
CASH AND CASH EQUIVALENTS, end of year	645,830	232,297	115,771
Reportable legal entities | Guarantor Subsidiaries and KDSM, LLC
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES	599,761	721,991	530,768
CASH FLOWS USED IN INVESTING ACTIVITIES:
Acquisition of property and equipment	(68,475)	(82,450)	(84,079)
Acquisition of businesses, net of cash acquired	(262,965)	(415,482)	(17,011)
Purchase of alarm monitoring contracts	0	0	0
Proceeds from the sale of assets	0	7,263	23,650
Investments in equity and cost method investees	(20,701)	(27)	(27)
Other, net	768	3,985	575
Net cash flow used in investing activities	(351,373)	(486,711)	(76,892)
CASH FLOWS FROM (USED IN) 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	(1,865)	(1,633)	(1,286)
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
Noncontrolling interests distributions	0	0	0
Increase (decrease) in intercompany payables	(242,402)	(224,551)	(452,897)
Other, net	(2,523)	1,344	(1,207)
Net cash flows from (used in) financing activities	(246,790)	(224,840)	(455,390)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	1,598	10,440	(1,514)
CASH AND CASH EQUIVALENTS, beginning of year	10,675	235
CASH AND CASH EQUIVALENTS, end of year	12,273	10,675	235
Reportable legal entities | Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES	12,424	7,914	(16,864)
CASH FLOWS USED IN INVESTING ACTIVITIES:
Acquisition of property and equipment	(2,930)	(5,009)	(2,586)
Acquisition of businesses, net of cash acquired	0	(10,375)	0
Purchase of alarm monitoring contracts	(5,682)	(40,206)	(39,185)
Proceeds from the sale of assets	192,634	9,133	0
Investments in equity and cost method investees	(32,762)	(32,655)	(35,690)
Other, net	6,321	5,072	17,645
Net cash flow used in investing activities	157,581	(74,040)	(59,816)
CASH FLOWS FROM (USED IN) FINANCING ACTIVITIES:
Proceeds from notes payable, commercial bank financing and capital leases	7,128	29,912	33,325
Repayments of notes payable, commercial bank financing and capital leases	(120,717)	(19,160)	(10,642)
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		(251)	(243)
Noncontrolling interests distributions	(22,416)	(10,464)	(9,918)
Increase (decrease) in intercompany payables	(25,605)	49,403	85,953
Other, net	(2,184)	(268)	(368)
Net cash flows from (used in) financing activities	(163,794)	49,172	98,107
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	6,211	(16,954)	21,427
CASH AND CASH EQUIVALENTS, beginning of year	17,012	33,966
CASH AND CASH EQUIVALENTS, end of year	23,223	17,012	33,966
Eliminations
Condensed Financial Statements, Captions [Line Items]
NET CASH FLOWS (USED IN) FROM OPERATING ACTIVITIES	8,544	23,875	24,145
CASH FLOWS USED IN INVESTING ACTIVITIES:
Acquisition of property and equipment	2,696	1,000	1,849
Acquisition of businesses, net of cash acquired	0	0	0
Purchase of alarm monitoring contracts	0	0	0
Proceeds from the sale of assets	0	0	0
Investments in equity and cost method investees	0	0	0
Other, net	0	0	0
Net cash flow used in investing activities	2,696	1,000	1,849
CASH FLOWS FROM (USED IN) 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	0	0
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
Noncontrolling interests distributions	0	0	0
Increase (decrease) in intercompany payables	(11,560)	(25,128)	(26,130)
Other, net	320	253	136
Net cash flows from (used in) financing activities	(11,240)	(24,875)	(25,994)
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	0	0	0
CASH AND CASH EQUIVALENTS, beginning of year	0	0
CASH AND CASH EQUIVALENTS, end of year	$ 0	$ 0	$ 0