Earnings Per Share - 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, 2026	Feb. 28, 2025	Feb. 28, 2026	Feb. 28, 2025
Numerator for earnings per share:
Net Income (Loss)		$ 51,364	$ 52,034	$ 440,176	$ 462,930
Less: Allocation of earnings and dividends to participating securities		(273)	(256)	(1,733)	(1,788)
Net income available to common shareholders - basic		51,091	51,778	438,443	461,142
Add: Undistributed earnings reallocated to unvested shareholders		0	0	4	6
Net income available to common shareholders - diluted		$ 51,091	$ 51,778	$ 438,447	$ 461,148
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		127,045	127,536	127,156	127,628
Average diluted options and awards		462	618	551	687
Total shares for diluted earnings per share	[1]	127,507	128,154	127,707	128,315
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock		$ 0.4	$ 0.41	$ 3.45	$ 3.61
Method used to calculate basic earnings per share		Two-class	Two-class	Two-class	Two-class
Diluted Earnings Per Share of Common Stock		$ 0.4	$ 0.4	$ 3.43	$ 3.59
Method used to calculate diluted earnings per share		Two-class	Two-class	Two-class	Two-class

[1] The dilutive effect of performance-based restricted stock units is included when they have met minimum performance thresholds. The dilutive effect of SARs includes all outstanding awards except awards that are considered antidilutive. SARs are antidilutive when the exercise price exceeds the average market price of the Company’s common shares during the periods presented. For the three and nine months ended February 28, 2026, approximately 460,000 and 420,000 shares of stock, respectively, granted under stock-based compensation plans were excluded from the calculation of diluted EPS, as the effect would have been anti-dilutive. For the three and nine months ended February 28, 2025, approximately 190,000 and 170,000 shares of stock, respectively, granted under stock-based compensation plans were excluded from the calculation of diluted EPS, as the effect would have been anti-dilutive.