Reconciliation of Numerator and Denominator of Basic and Diluted Earnings Per Share, Calculated using Two-Class Method (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Feb. 28, 2014		Feb. 28, 2013		Feb. 28, 2014		Feb. 28, 2013
Numerator for earnings per share:
Net income (loss) attributable to RPM International Inc. stockholders	$ 16,221		$ (42,356)		$ 182,881		$ 33,225
Less: Allocation of earnings and dividends to participating securities	(299)				(3,897)		(510)
Net income (loss) available to common shareholders - basic	15,922		(42,356)		178,984		32,715
Add: Undistributed earnings reallocated to unvested shareholders					15		(8)
Add: Income effect of contingently issuable shares					1,202
Net income (loss) available to common shareholders -diluted	$ 15,922		$ (42,356)		$ 180,201		$ 32,707
Denominator for basic and diluted earnings per share:
Basic weighted average common shares	129,453		129,013		129,407		128,900
Average diluted options					999		822
Net issuable common share equivalents
Additional shares issuable assuming conversion of convertible securities					1,163
Total shares for diluted earnings per share	129,453	[1],[2]	129,013	[1],[2]	131,569	[1],[2]	129,722	[1],[2]
Earnings per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings (Loss) Per Share of Common Stock	$ 0.12		$ (0.33)		$ 1.38		$ 0.25
Diluted Earnings (Loss) Per Share of Common Stock	$ 0.12		$ (0.33)		$ 1.37		$ 0.25

[1] For the quarter ended February 28, 2014, basic weighted-average shares outstanding and basic net income available to common shareholders are used in calculating diluted earnings per share under the two-class method, as that method resulted in the most dilutive earnings per share.

[2] For the quarter ended February 28, 2013, basic weighted-average shares outstanding are used in calculating diluted earnings per share under the treasury stock method, as the result under the two-class method would have been anti-dilutive.