XML 45 R34.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions | 6 Months Ended | 12 Months Ended
--- | --- | ---
Nov. 30, 2015 | May. 31, 2015
Fair value on a recurring basis |  |
Contractual maturities (less than) | 1 year | 1 year
Canadian treasury securities |  |
Fair value on a recurring basis |  |
Amortized cost basis of marketable securities | $ 65.8 | $ 16.1

X
- Definition Available-for-sale Securities, Debt Maturities, Term + References No definition available. + Details
Name: | ctas_AvailableforsaleSecuritiesDebtMaturitiesTerm
Namespace Prefix: | ctas_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Details
Name: | us-gaap_InvestmentTypeAxis=ctas_CanadianTreasurySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |