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, 2019	Feb. 28, 2018	Feb. 28, 2019	Feb. 28, 2018
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders		$ 14,190	$ 40,227	$ 133,178	$ 252,106
Less: Allocation of earnings and dividends to participating securities		(109)	(530)	(996)	(3,373)
Net income available to common shareholders - basic		14,081	39,697	132,182	248,733
Add: Undistributed earnings reallocated to unvested shareholders					7
Add: Allocation of earnings and dividends to participating securities		109		996
Add: Income effect of contingently issuable shares					4,351
Net income available to common shareholders - diluted		$ 14,190	$ 39,697	$ 133,178	$ 253,091
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		130,105	131,178	131,019	131,195
Average diluted options and awards		1,784		1,810	540
Additional shares issuable assuming conversion of convertible securities	[1]				3,922
Total shares for diluted earnings per share	[2]	131,889	131,178	132,829	135,657
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock		$ 0.11	$ 0.30	$ 1.01	$ 1.90
Diluted Earnings Per Share of Common Stock		$ 0.11	$ 0.30	$ 1.00	$ 1.87

[1] Represents the number of shares that would have been 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

[2] Restricted shares totaling 429,750 and 323,000 for the three and nine months ended February 28, 2019, respectively, and restricted shares totaling 48,212 for the three and nine months ended February 28, 2018 were excluded from the calculation of diluted earnings per share because the grant price of the restricted shares exceeded the average market price of the shares during the period and their effect, accordingly, would have been anti-dilutive. In addition, stock appreciation rights (SARs) totaling 890,000 for the three and nine months ended February 28, 2019 and 600,000 for the three and nine months ended February 28, 2018, were excluded from the calculation of diluted earnings per share as their effect would have been anti-dilutive.