Document And Entity Information - shares	6 Months Ended
	Feb. 29, 2016	Mar. 28, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Feb. 29, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q2
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		48,552,214