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.

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

+ Details

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Data Type:	num: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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120397183&loc=d3e187085-122770

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-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=120397183&loc=d3e187085-122770

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

- Details

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Data Type:	na
Balance Type:
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- Details

Name:	us-gaap_ShareRepurchaseProgramAxis=ctas_ShareBuybackProgramOctober2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
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- Details

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Earnings per Share - Summary of Buyback Activity by Program (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended		28 Months Ended
	Feb. 28, 2021	Nov. 30, 2020	Aug. 31, 2020	Feb. 29, 2020	Nov. 30, 2019	Aug. 31, 2019	Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021
Equity, Class of Treasury Stock [Line Items]
Stock purchased under share buyback	$ 83,108	$ 2,371	$ 69,011	$ 2,586	$ 1,911	$ 256,830
Share Buyback Programs
Equity, Class of Treasury Stock [Line Items]
Stock purchased under share buyback (shares)	256			0			256	837
Stock purchased under share buyback, average price (in dollars per share)	$ 320.30			$ 0			$ 320.30	$ 230.66
Stock purchased under share buyback	$ 81,957			$ 0			$ 81,957	$ 193,109
October 30, 2018 Plan
Equity, Class of Treasury Stock [Line Items]
Stock purchased under share buyback (shares)	190			0			190	837	4,500
Stock purchased under share buyback, average price (in dollars per share)	$ 319.88			$ 0			$ 319.88	$ 230.66	$ 223.68
Stock purchased under share buyback	$ 60,877			$ 0			$ 60,877	$ 193,109	$ 1,000,000
October 29, 2019 Plan
Equity, Class of Treasury Stock [Line Items]
Stock purchased under share buyback (shares)	66			0			66	0
Stock purchased under share buyback, average price (in dollars per share)	$ 321.51			$ 0			$ 321.51	$ 0
Stock purchased under share buyback	$ 21,080			$ 0			$ 21,080	$ 0