This element represents the maximum borrowing capacity under a commercial paper program.

No definition available.

Name:	ctas_CommercialPaperMaximumBorrowingCapacity
Namespace Prefix:	ctas_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	ctas_DebtDerivativesAndHedgingActivitiesDisclosureAbstract
Namespace Prefix:	ctas_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the denominator for the ratio of consolidated indebtedness to consolidated EBITDA (earnings before interest, taxes, depreciation and amortization) ratio permitted under financial covenants.

+ References

No definition available.

+ Details

Name:	ctas_DebtInstrumentCovenantRatioConsolidatedIndebtednessToConsolidatedEBITDADenominator
Namespace Prefix:	ctas_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the numerator for the ratio of consolidated indebtedness to consolidated EBITDA (earnings before interest, taxes, depreciation and amortization) ratio permitted under financial covenants.

+ References

No definition available.

+ Details

Name:	ctas_DebtInstrumentCovenantRatioConsolidatedIndebtednessToConsolidatedEBITDANumerator
Namespace Prefix:	ctas_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the increase in comprehensive income related to the amortization of an interest rate cash flow hedge.

+ References

No definition available.

+ Details

Name:	ctas_OtherComprehensiveIncomeIncreaseFromAmortizationOfInterestRateCashFlowHedge
Namespace Prefix:	ctas_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 129

-Paragraph 2, 4

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

Debt, Derivatives and Hedging Activities (Details) (USD $)	3 Months Ended		9 Months Ended
	Feb. 29, 2012	Feb. 28, 2011	Feb. 29, 2012	Feb. 28, 2011
Debt, Derivatives and Hedging Activities
Commercial paper program availability	$ 300,000,000		$ 300,000,000
Revolving credit facility, maximum borrowing capacity with accordion feature	450,000,000		450,000,000
Debt, Derivatives and Hedging Activities
Increase to other comprehensive income resulting from amortization of the interest rate lock agreements	$ 377,000	$ 192,000	$ 1,131,000	$ 575,000
No more than
Debt, Derivatives and Hedging Activities
Numerator for the ratio of consolidated indebtedness to consolidated EBITDA			3.5
Denominator for the ratio of consolidated indebtedness to consolidated EBITDA			1.0