Earnings Per Share - Summary of Buyback Activity by Program (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
Aug. 31, 2023	Aug. 31, 2022
Equity, Class of Treasury Stock [Line Items]
Stock purchased under share buyback	$ 73,276	$ 320,334
Shares acquired for taxes due (in shares)	145	270
Shares acquired for taxes due, average price (in dollars per share)	$ 503.20	$ 405.93
Shares acquired for taxes due	$ 73,276	$ 109,583
Total repurchase of Cintas common stock	$ 73,276	$ 320,334
Share Buyback Programs
Equity, Class of Treasury Stock [Line Items]
Stock purchased under share buyback (in shares)	0	532
Stock purchased under share buyback, average price (in dollars per share)	$ 0	$ 396.39
Stock purchased under share buyback	$ 0	$ 210,751
July 27, 2021 Plan
Equity, Class of Treasury Stock [Line Items]
Stock purchased under share buyback (in shares)	0	532
Stock purchased under share buyback, average price (in dollars per share)	$ 0	$ 396.39
Stock purchased under share buyback	$ 0	$ 210,751
July 26, 2022 Plan
Equity, Class of Treasury Stock [Line Items]
Stock purchased under share buyback (in shares)	0	0
Stock purchased under share buyback, average price (in dollars per share)	$ 0	$ 0
Stock purchased under share buyback	$ 0	$ 0

Share-Based Payment Arrangement, Shares Withheld For Tax Withholding Obligation, Average Cost

No definition available.

Name:	ctas_ShareBasedPaymentArrangementSharesWithheldForTaxWithholdingObligationAverageCost
Namespace Prefix:	ctas_
Data Type:	dtr-types1:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Treasury Stock, Value, Acquired, Cost Method, And Share Based Payment Arrangement, Decrease For Tax Withholding Obligation

+ References

No definition available.

+ Details

Name:	ctas_TreasuryStockValueAcquiredCostMethodAndShareBasedPaymentArrangementDecreaseForTaxWithholdingObligation
Namespace Prefix:	ctas_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of decrease to equity for grantee's tax withholding obligation for award under share-based payment arrangement.

+ References

No definition available.

+ Details

Name:	us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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_EquityClassOfTreasuryStockLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares used to settle grantee's tax withholding obligation for award under share-based payment arrangement.

+ References

No definition available.

+ Details

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

- Definition

Total cost of shares repurchased divided by the total number of shares repurchased.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481549/505-30-45-1

+ Details

Name:	us-gaap_TreasuryStockAcquiredAverageCostPerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares that have been repurchased during the period and are being held in treasury.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-SubTopic 10
-Topic 505
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-2

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1

+ Details

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

- Definition

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-SubTopic 10
-Topic 505
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481112/505-10-50-2

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481549/505-30-45-1

+ Details

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

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=ctas_ShareBuybackProgramsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=ctas_ShareBuybackProgramJuly272021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=ctas_ShareBuybackProgramJuly262022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: