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		6 Months Ended
		Nov. 30, 2025	Nov. 30, 2024	Nov. 30, 2025	Nov. 30, 2024
Numerator for earnings per share:
Net Income (Loss)		$ 161,207	$ 183,204	$ 388,812	$ 410,896
Less: Allocation of earnings and dividends to participating securities		(701)	(739)	(1,587)	(1,615)
Net income available to common shareholders - basic		160,506	182,465	387,225	409,281
Add: Undistributed earnings reallocated to unvested shareholders		1	3	5	7
Net income available to common shareholders - diluted		$ 160,507	$ 182,468	$ 387,230	$ 409,288
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		127,129	127,658	127,206	127,675
Average diluted options and awards		520	686	593	717
Total shares for diluted earnings per share	[1]	127,649	128,344	127,799	128,392
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock		$ 1.26	$ 1.43	$ 3.04	$ 3.21
Method used to calculate basic earnings per share		Two-class	Two-class	Two-class	Two-class
Diluted Earnings Per Share of Common Stock		$ 1.26	$ 1.42	$ 3.03	$ 3.19
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 six months ended November 30, 2025, approximately 580,000 and 480,000 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 six months ended November 30, 2024, approximately 300,000 and 230,000 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.