Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended
Aug. 31, 2020	Aug. 31, 2019
Statement Of Stockholders Equity [Abstract]
Dividends declared and paid per share	$ 0.36	$ 0.35

Common stock dividends declared and paid per share.

No definition available.

Name:	rpm_CommonStockDividendsDeclaredAndPaidPerShare
Namespace Prefix:	rpm_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration