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		6 Months Ended
		Nov. 30, 2021	Nov. 30, 2020	Nov. 30, 2021	Nov. 30, 2020
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders		$ 124,875	$ 127,659	$ 259,457	$ 308,254
Less: Allocation of earnings and dividends to participating securities		(1,103)	(1,130)	(2,198)	(2,517)
Net income available to common shareholders - basic		123,772	126,529	257,259	305,737
Add: Undistributed earnings reallocated to unvested shareholders		2	4	6	9
Net income available to common shareholders - diluted		$ 123,774	$ 126,533	$ 257,265	$ 305,746
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		128,022	128,500	128,058	128,459
Average diluted options and awards		472	590	479	619
Total shares for diluted earnings per share	[1]	128,494	129,090	128,537	129,078
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Earnings Per Share Basic		$ 0.97	$ 0.98	$ 2.01	$ 2.38
Method used to calculate basic earnings per share		Two-class	Two-class	Two-class	Two-class
Earnings Per Share Diluted		$ 0.96	$ 0.98	$ 2.00	$ 2.37
Method used to calculate diluted earnings per share		Two-class	Two-class	Two-class	Two-class

[1] For the three and six months ended November 30, 2021, no restricted shares were excluded from the calculation of diluted earnings per share as their effect would have been anti-dilutive. For the three and six months ended November 30, 2020, restricted shares totaling 225,500 and 339,550 were excluded from the calculation of diluted earnings per share as their effect would have been anti-dilutive. In addition, stock appreciation rights (“SARs”) totaling 660,000 for both the three and six months ended November 30, 2021, and 360,000 for both the three and six months ended November 30, 2020, were excluded from the calculation of diluted earnings per share as their effect would have been anti-dilutive.