DebtInstrumentExtensionPeriod

No definition available.

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Namespace Prefix:	sonc_
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Balance Type:	na
Period Type:	duration

- Definition

DebtInstrumentLegalFinalMaturityYear

+ References

No definition available.

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument Number Of Extensions

+ References

No definition available.

+ Details

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Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Expected life of debt instrument.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

LongTermDebtFixedRateNotesIncludingAccruedInterestCarryingValue

+ References

No definition available.

+ Details

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Namespace Prefix:	sonc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Debt Prepayment Premium paid due to early extinguishment of debt

+ References

No definition available.

+ Details

Name:	sonc_Prepaymentpremium
Namespace Prefix:	sonc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.18)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 12
-Article 7

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

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-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Date the debt instrument was issued, in CCYY-MM-DD format.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Net amount of long-term deferred finance costs capitalized at the end of the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28555-108399

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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12317-112629

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-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=49170532&loc=d3e12355-112629

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of long-term debt outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

+ References

No definition available.

+ Details

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Balance Type:	debit
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- Definition

The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element.

+ References

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Balance Type:	debit
Period Type:	instant

- Definition

Write-off of amounts previously capitalized as debt issuance cost in an extinguishment of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.8)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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- Details

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- Details

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- Details

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- Details

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Debt (Details)	3 Months Ended	9 Months Ended
Debt (Details)	May 31, 2016 USD ($)	May 31, 2016 USD ($)	May 31, 2015 USD ($)	May 17, 2016 USD ($)	Aug. 31, 2015 USD ($)
Debt Instrument [Line Items]
Total assets	$ 679,666,000	$ 679,666,000			$ 620,024,000
Debt origination costs, net	14,996,000	14,996,000			$ 7,056,000
Debt extinguishment costs	8,750,000	8,750,000
Prepayment Premium	5,900,000	5,900,000
Write-off of unamortized debt origination costs		2,900,000
Proceeds from Issuance of Debt		563,000,000	$ 67,500,000
Co-Issuers and Guarantor [Member]
Debt Instrument [Line Items]
Total assets	315,400,000	315,400,000
Restricted cash	11,000,000	$ 11,000,000
2016 Notes [Member]
Debt Instrument [Line Items]
Debt issuance date		May 17, 2016
Debt instrument, legal final maturity year		May 20, 2046
Debt origination costs, net	$ 12,600,000	$ 12,600,000
2016 Fixed Rate Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 425,000,000
Senior secured notes interest rate, percentage	4.47%	4.47%
Expected life of debt instrument		7 years
Long-term debt, carrying value, including accrued interest	$ 425,700,000	$ 425,700,000
Weighted-average interest cost, percentage	4.79%	4.79%
Debt Instrument, Maturity Date		May 20, 2023
Interest Rate Upward Adjustment Due To Nonpayment [Member]
Debt Instrument [Line Items]
Senior secured notes interest rate, percentage	5.00%	5.00%
2016 Variable Funding Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 150,000,000
Interest rate spread		2.00%
Annual commitment fee payable, percentage		0.50%
Expected life of debt instrument		5 years
Debt instrument, number of extensions	2	2
Debt instrument, extension period		1 year
Long-term debt, carrying value, including accrued interest	$ 0	$ 0
Debt Instrument, Maturity Date		May 20, 2021