XML 91 R77.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Employee Benefit Plans - Asset allocations in the pension plan (Details) | May 31, 2018 | May 31, 2017
--- | --- | ---
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocations (as a percent) | 100.00% |
Actual Asset Allocations (as a percent) | 100.00% | 100.00%
International equity |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocations (as a percent) | 8.00% |
Actual Asset Allocations (as a percent) | 7.90% | 8.30%
Large cap equity |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocations (as a percent) | 26.00% |
Actual Asset Allocations (as a percent) | 26.50% | 26.30%
Small cap equity |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocations (as a percent) | 5.00% |
Actual Asset Allocations (as a percent) | 5.60% | 5.30%
Absolute return strategy funds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocations (as a percent) | 16.00% |
Actual Asset Allocations (as a percent) | 15.80% | 16.20%
Fixed income |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocations (as a percent) | 45.00% |
Actual Asset Allocations (as a percent) | 44.20% | 43.60%
Long/short equity fund |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocations (as a percent) | 0.00% |
Actual Asset Allocations (as a percent) | 0.00% | 0.30%

X
- 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_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanPlanAssetsTargetAllocationPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanWeightedAverageAssetAllocations
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ctas_InternationalEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ctas_LargeCapEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ctas_SmallCapEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ctas_AbsoluteReturnStrategyFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ctas_FixedIncomeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=ctas_LongShortEquityFundMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |