Document And Entity Information	3 Months Ended
	Nov. 30, 2012	Dec. 28, 2012
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Nov. 30, 2012
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1
Entity Registrant Name	SONIC CORP
Entity Central Index Key	0000868611
Current Fiscal Year End Date	--08-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		55,630,107