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. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders		$ 11,853	$ 14,190	$ 195,072	$ 133,178
Less: Allocation of earnings and dividends to participating securities			(109)	(1,199)	(996)
Net income available to common shareholders - basic		11,853	14,081	193,873	132,182
Add: Allocation of earnings and dividends to participating securities			109	2	996
Net income available to common shareholders - diluted		$ 11,853	$ 14,190	$ 193,875	$ 133,178
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		128,426	130,105	128,572	131,019
Average diluted options and awards		1,602	1,784	666	1,810
Total shares for diluted earnings per share	[1]	130,028	131,889	129,238	132,829
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock		$ 0.09	$ 0.11	$ 1.51	$ 1.01
Method used to calculate basic earnings per share		Treasury	Two-class	Two-class	Two-class
Diluted Earnings Per Share of Common Stock		$ 0.09	$ 0.11	$ 1.50	$ 1.00
Method used to calculate diluted earnings per share		Treasury	Treasury	Two-class	Treasury

[1] There were no shares of restricted stock identified as being anti-dilutive for the three or nine months ended February 29, 2020.  Restricted shares totaling 429,750 and 323,000 for the three and nine months ended February 28, 2019, respectively, were excluded from the calculation of diluted earnings per share as their effect would have been anti-dilutive.