Reconciliation of Numerator and Denominator of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		12 Months Ended
		May 31, 2021	May 31, 2020	May 31, 2019
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders		$ 502,643	$ 304,385	$ 266,558
Less: Allocation of earnings and dividends to participating securities		(4,018)	(1,956)	(1,514)
Net income available to common shareholders - basic		498,625	302,429	265,044
Reverse: Allocation of earnings and dividends to participating securities			1,956	1,514
Add: Undistributed earnings reallocated to unvested shareholders		13
Add: Income effect of contingently issuable shares				3,655
Net income available to common shareholders - diluted		$ 498,638	$ 304,385	$ 270,213
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		128,334	128,468	130,552
Average diluted options		593	1,506	1,838
Net issuable common share equivalents	[1]			1,943
Total shares for diluted earnings per share	[2]	128,927	129,974	134,333
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock		$ 3.89	$ 2.35	$ 2.03
Method used to calculate basic earnings per share		Two-Class	Two-Class	Two-Class
Diluted Earnings Per Share of Common Stock		$ 3.87	$ 2.34	$ 2.01
Method used to calculate diluted earnings per share		Two-Class	Treasury	Treasury

[1] Represents the number of shares that would be issued if our contingently convertible notes had been converted.  We included these shares in the calculation of diluted EPS as the conversion of the notes were eligible to be settled, at our election, in cash, shares of our common stock, or a combination of cash and shares of our common stock.  On November 27, 2018, we redeemed all of our 2.25% convertible senior notes due 2020, primarily for cash, but also issued 598,601 shares of our common stock in the transaction.

[2] For the years ended May 31, 2021, 2020 and 2019, approximately 362,016, 340,000 and 862,500 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.