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Pension Plans - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 3 Months Ended
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Aug. 31, 2012
Pension Benefits, U.S. Plans |
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items] |
Contribution to retirement plans in current fiscal year | $ 29.9
Pension Benefits, Non-U.S. Plans |
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items] |
Contribution to retirement plans in current fiscal year | $ 8.3

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- Details
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Namespace Prefix: | rpm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount of employer's best estimate of contributions expected to be paid to the plan in the current remaining fiscal period. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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