XML 26 R18.htm IDEA: XBRL DOCUMENT v2.4.1.9
Contingencies (Details) (USD $)
In Millions, unless otherwise specified
6 Months Ended
Feb. 28, 2015
Note Repurchase Agreement [Member]  
Loss Contingencies [Line Items]  
Guaranteed obligations $ 6.1us-gaap_GuaranteeObligationsMaximumExposure
/ us-gaap_GuaranteeObligationsByNatureAxis
= us-gaap_FinancialGuaranteeMember
Guarantor Obligations, Term 2018
Guarantee Operating Lease Obligations [Member]  
Loss Contingencies [Line Items]  
Guaranteed obligations 8.3us-gaap_GuaranteeObligationsMaximumExposure
/ us-gaap_GuaranteeObligationsByNatureAxis
= sonc_GuaranteeOperatingLeaseObligationsMember
Guaranteed liability, carrying value $ 0us-gaap_GuaranteeObligationsCurrentCarryingValue
/ us-gaap_GuaranteeObligationsByNatureAxis
= sonc_GuaranteeOperatingLeaseObligationsMember
Guarantor Obligations, Term 2029