Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Nov. 05, 2018
Entity Information [Line Items]
Entity Registrant Name	SINCLAIR BROADCAST GROUP INC
Entity Central Index Key	0000912752
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Document Type	10-Q
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	Q3
Amendment Flag	false
Class A Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding (shares)		71,792,701
Class B Common Stock
Entity Information [Line Items]
Entity Common Stock, Shares Outstanding (shares)		25,670,684