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, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders		$ 40,227	$ 11,928	$ 252,106	$ 53,771
Less: Allocation of earnings and dividends to participating securities		(530)	(232)	(3,373)	(847)
Net income available to common shareholders - basic		39,697	11,696	248,733	52,924
Add: Undistributed earnings reallocated to unvested shareholders				7
Add: Income effect of contingently issuable shares				4,351
Net income available to common shareholders - diluted		$ 39,697	$ 11,696	$ 253,091	$ 52,924
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		131,178	130,677	131,195	130,657
Average diluted options				540
Additional shares issuable assuming conversion of convertible securities	[1]			3,922
Total shares for diluted earnings per share	[2]	131,178	130,677	135,657	130,657
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock		$ 0.30	$ 0.09	$ 1.90	$ 0.41
Diluted Earnings Per Share of Common Stock		$ 0.30	$ 0.09	$ 1.87	$ 0.41

[1] Represents the number of shares that would be issued if our contingently convertible notes were converted. We include these shares in the calculation of diluted EPS as the conversion of the notes may be settled, at our election, in cash, shares of our common stock, or a combination of cash and shares of our common stock.

[2] 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. There were no restricted shares identified as being anti-dilutive for the three and nine months ended February 28, 2017. In addition, stock appreciation rights (SARs) totaling 600,000 for the three and nine months ended February 28, 2018 and 2017 were excluded from the calculation of diluted earnings per share as their effect would have been anti-dilutive.