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

Represents the average price of common stock that has been repurchased during the period under share repurchase program.

+ References

No definition available.

+ Details

Name:	ctas_StockRepurchasedDuringPeriodAveragePrice
Namespace Prefix:	ctas_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The new amount authorized by the entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

+ Details

Name:	ctas_StockRepurchaseProgramNewAuthorizedAmount
Namespace Prefix:	ctas_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Antidilution

-URI http://asc.fasb.org/extlink&oid=6505113

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Diluted Earnings Per Share

-URI http://asc.fasb.org/extlink&oid=6510752

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Contingent Stock Agreement

-URI http://asc.fasb.org/extlink&oid=6508534

+ Details

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

- Definition

Per basic and diluted share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation, when the per share amount is the same.

+ References

No definition available.

+ Details

Name:	us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicAndDilutedShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Per basic share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 260

-SubTopic 10

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e1278-109256

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.21)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.19)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.23)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 18

-Article 7

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 20

-Article 5

Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 21

-Article 9

+ Details

Name:	us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerBasicShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Per diluted share amount, after tax, of income (loss) from the day-to-day business activities of the discontinued operation and gain (loss) from the disposal of the discontinued operation.

+ References

+ Details

Name:	us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTaxPerDilutedShare
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

+ Details

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

- Definition

Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

+ Details

Name:	us-gaap_StockRepurchasedDuringPeriodValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_PlanNameAxis=ctas_BuybackProgramJuly2013Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementEquityComponentsAxis=us-gaap_CommonStockMember
Namespace Prefix:
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Period Type:

Earnings Per Share - Narrative (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended		1 Months Ended	18 Months Ended
	Nov. 30, 2014	Nov. 30, 2013	Nov. 30, 2014	Nov. 30, 2013	Jan. 09, 2015	Jan. 09, 2015	Jul. 30, 2013
Earnings Per Share, Basic and Diluted [Line Items]
Basic earnings per share, discontinued operations (dollars per share)	$ 0.15	$ 0.01	$ 0.15	$ 0.01
Diluted earnings per share, discontinued operations (dollars per share)	$ 0.14	$ 0.01	$ 0.14	$ 0.01
Basic and Diluted earnings per share from discontinued operations (shares)		$ 0.01		$ 0.01
Options granted and excluded from the computation of diluted earnings per share (shares)	500,000	500,000	600,000	700,000
Common Stock
Earnings Per Share, Basic and Diluted [Line Items]
Common stock purchased under a share buyback program (shares)	0		800,000
Aggregate purchase price of common stock under a share buyback program			$ 49.7
Average price of common stock purchased under a share buyback program (dollars per share)			$ 62.17
Common Stock \| Employee payroll taxes due on restricted stock
Earnings Per Share, Basic and Diluted [Line Items]
Common stock purchased under a share buyback program (shares)			200,000
Aggregate purchase price of common stock under a share buyback program	2.2		13.9
Average price of common stock purchased under a share buyback program (dollars per share)			$ 64.07
Common Stock \| Subsequent Event
Earnings Per Share, Basic and Diluted [Line Items]
Common stock purchased under a share buyback program (shares)					0	4,100,000
Aggregate purchase price of common stock under a share buyback program						$ 249.2
Average price of common stock purchased under a share buyback program (dollars per share)						$ 60.19
July 30, 2013
Earnings Per Share, Basic and Diluted [Line Items]
Additional amount authorized under share buyback program (shares)							500,000,000