Amounts Recognized in Consolidated Balance Sheets, Postretirement (Detail) (USD $) In Thousands, unless otherwise specified	May 31, 2012	May 31, 2011
Postretirement Benefits, U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities	$ (714)	$ (672)
Noncurrent liabilities	(8,963)	(8,431)
Net Amount Recognized	(9,677)	(9,103)
Postretirement Benefits, Non-U.S. Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Current liabilities	(428)	(380)
Noncurrent liabilities	(24,089)	(17,177)
Net Amount Recognized	$ (24,517)	$ (17,557)

For classified balance sheets this represents the current liability recognized in the balance sheet that is associated with other postretirement defined benefit plans (excluding pension plans). (The current liability will be separate, but it will normally be small, if there is even any at all.) For unclassified balance sheets, this represents the entire liability recognized in the balance sheet that is associated with the plans.

No definition available.

Name:	rpm_OtherPostretirementDefinedBenefitPlanCurrentLiabilities
Namespace Prefix:	rpm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant