Document And Entity Information	9 Months Ended
	May 31, 2012	Jul. 02, 2012
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	May 31, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q3
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		58,058,345