Name:	cosi_AdditionalVestingRightsPercentageOnEachAnniversaryOfGrantDate
Namespace Prefix:	cosi_
Data Type:	num:percentItemType
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consecutive trading days for which closing price of the Company's common stock shall have exceeded specified price.

No definition available.

Name:	cosi_ConsecutiveTradingDays
Namespace Prefix:	cosi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents number of installments in which restricted common stock vest.

No definition available.

Name:	cosi_NumberOfInstallmentsInWhichRestrictedCommonStockVest
Namespace Prefix:	cosi_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Number of restricted shares granted with specified vesting schedule.

No definition available.

Name:	cosi_RestrictedSharesGrantedWithSpecifiedVestingSchedule
Namespace Prefix:	cosi_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

Vesting percentage on first day on which the closing price of the Company's common stock shall have exceeded specified amount for 30 consecutive trading days (as adjusted for stock splits, recapitalizations, reorganizations or similar events).

No definition available.

Name:	cosi_VestingPercentageOnEachSpecifiedClosingPrice
Namespace Prefix:	cosi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

No definition available.

Name:	cosi_VestingRightsPercentageOnGrantDate
Namespace Prefix:	cosi_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Unrecognized cost of unvested options awarded to employees as compensation.

No definition available.

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

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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

- Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Price of a single share of a number of saleable stocks of a company.

No definition available.

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Value of forfeitures of stock or other type of equity granted of any equity-based compensation plan other than an employee stock ownership plan (ESOP).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph c(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Name:	us-gaap_StockGrantedDuringPeriodValueSharebasedCompensationForfeited
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Value, before forfeitures, of stock or other type of equity granted of any equity-based compensation plan other than an employee stock ownership plan (ESOP).

No definition available.

Name:	us-gaap_StockGrantedDuringPeriodValueSharebasedCompensationGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Total number of shares issued during the period, including shares forfeited, as a result of Restricted Stock Awards.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770