Document and Entity Information - USD ($)
12 Months Ended
May 31, 2018
Jul. 19, 2018
Nov. 30, 2017
Document And Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date May 31, 2018    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Trading Symbol RPM    
Entity Registrant Name RPM INTERNATIONAL INC/DE/    
Entity Central Index Key 0000110621    
Current Fiscal Year End Date --05-31    
Entity Well-known Seasoned Issuer Yes    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Filer Category Large Accelerated Filer    
Entity Common Stock, Shares Outstanding   133,482,764  
Entity Public Float     $ 6,972,779,525