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																12 Months Ended
		May 31, 2020		Feb. 29, 2020		Nov. 30, 2019		Aug. 31, 2019		May 31, 2019		Feb. 28, 2019		Nov. 30, 2018		Aug. 31, 2018		May 31, 2020	May 31, 2019	May 31, 2018
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders		$ 109,314	[1]	$ 11,853	[1]	$ 77,030	[1]	$ 106,188	[1]	$ 133,380	[2]	$ 14,190	[2]	$ 49,224	[2]	$ 69,764	[2]	$ 304,385	$ 266,558	$ 337,770
Less: Allocation of earnings and dividends to participating securities																		(1,956)	(1,514)	(3,858)
Net income available to common shareholders - basic																		302,429	265,044	333,912
Reverse: Allocation of earnings and dividends to participating securities																		1,956	1,514	3,858
Add: Income effect of contingently issuable shares																			3,655	5,673
Net income available to common shareholders - diluted																		$ 304,385	$ 270,213	$ 343,443
Denominator for basic and diluted earnings per share:
Basic weighted average common shares																		128,468	130,552	131,179
Average diluted options																		1,506	1,838	2,064
Net issuable common share equivalents	[3]																		1,943	3,928
Total shares for diluted earnings per share	[4]																	129,974	134,333	137,171
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Method used to calculate basic earnings per share																		Two-Class	Two-Class	Two-Class
Method used to calculate diluted earnings per share																		Treasury	Treasury	Treasury
Basic Earnings Per Share of Common Stock		$ 0.85		$ 0.09		$ 0.60		$ 0.82		$ 1.03		$ 0.11		$ 0.37		$ 0.52		$ 2.35	$ 2.03	$ 2.55
Diluted Earnings Per Share of Common Stock		$ 0.84		$ 0.09		$ 0.59		$ 0.82		$ 1.02		$ 0.11		$ 0.37		$ 0.52		$ 2.34	$ 2.01	$ 2.50

[1] Reflects inventory-related charges of $28.8 million in our Consumer reportable segment resulting from SKU rationalization, excess and obsolescence, and exiting unprofitable product lines and regions and $3.2 million in our PCG segment resulting from the exit of unprofitable product lines and regions.  Also reflects restructuring charges totaling $33.1 million that were incurred throughout fiscal 2020, as further described in Note B, “Restructuring”.

[2] Reflects inventory-related charges of $10.5 million in our Consumer reportable segment resulting from more proactive management of inventory and $9.0 million and $1.0 million in inventory reductions related to restructuring activities in our PCG and CPG reportable segments, respectively.  Also reflects restructuring charges totaling $42.3 million that were incurred throughout fiscal 2019, as further described in Note B, “Restructuring”.

[3] 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

[4] For the years ended May 31, 2020, 2019 and 2018, approximately 340,000, 862,500 and 799,362 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.