Document And Entity Information	3 Months Ended
	Nov. 30, 2014	Jan. 02, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Nov. 30, 2014
Document Fiscal Year Focus	2015
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	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		53,517,843
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No