Document And Entity Information - shares	3 Months Ended
	Nov. 30, 2016	Jan. 03, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	SONIC CORP.
Entity Central Index Key	0000868611
Current Fiscal Year End Date	--08-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-Q
Document Period End Date	Nov. 30, 2016
Document Fiscal Year Focus	2017
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		43,934,660