Reconciliation of Numerator and Denominator of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Feb. 28, 2021	Feb. 29, 2020	Feb. 28, 2021	Feb. 29, 2020
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders		$ 38,242	$ 11,853	$ 346,496	$ 195,072
Less: Allocation of earnings and dividends to participating securities		(185)		(2,740)	(1,199)
Net income available to common shareholders - basic		38,057	11,853	343,756	193,873
Add: Undistributed earnings reallocated to unvested shareholders				9	2
Reverse: Allocation of earnings and dividends to participating securities		185
Net income available to common shareholders - diluted		$ 38,242	$ 11,853	$ 343,765	$ 193,875
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		128,447	128,426	128,455	128,572
Average diluted options and awards		1,502	1,602	597	666
Total shares for diluted earnings per share	[1]	129,949	130,028	129,052	129,238
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock		$ 0.30	$ 0.09	$ 2.68	$ 1.51
Method used to calculate basic earnings per share		Two-class	Treasury	Two-class	Two-class
Diluted Earnings Per Share of Common Stock		$ 0.29	$ 0.09	$ 2.66	$ 1.50
Method used to calculate diluted earnings per share		Treasury	Treasury	Two-class	Two-class

[1] Restricted shares totaling 225,500 and 231,450 for the three and nine months ended February 28, 2021, respectively, were excluded from the calculation of diluted earnings per share as their effect would have been anti-dilutive. There were no shares of restricted stock identified as being anti-dilutive for the three or nine months ended February 29, 2020.  In addition, stock appreciation rights (“SARs”) totaling 360,000 and for the three and nine months ended February 28, 2021 were excluded from the calculation of diluted earnings per share as their effect would have been anti-dilutive.  There were no SARs identified as being anti-dilutive for the three or nine months ended February 29, 2020.