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				6 Months Ended
	Nov. 30, 2012		Nov. 30, 2011		Nov. 30, 2012		Nov. 30, 2011
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders	$ 41,668		$ 49,931		$ 75,581		$ 126,742
Less: Allocation of earnings and dividends to participating securities	(929)		(979)		(1,526)		(2,297)
Net income available to common shareholders - basic	40,739		48,952		74,055		124,445
Add: Undistributed earnings reallocated to unvested shareholders	2		2		2		5
Net income available to common shareholders - diluted	$ 40,741		$ 48,954		$ 74,057		$ 124,450
Denominator for basic and diluted earnings per share:
Basic weighted average common shares	128,885		127,986		128,844		128,048
Average diluted options	815		446		791		489
Net issuable common share equivalents
Total shares for diluted earnings per share	129,700	[1],[2]	128,432	[1],[2]	129,635	[1],[2]	128,537	[1],[2]
Earnings per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock	$ 0.32		$ 0.38		$ 0.57		$ 0.97
Diluted Earnings Per Share of Common Stock	$ 0.31		$ 0.38		$ 0.57		$ 0.97

[1] For the quarters ended November 30, 2012 and 2011, approximately 3,151,000 shares and 2,722,000 shares of stock, respectively, granted under stock-based compensation plans were excluded from the calculation of diluted EPS for those periods, as the effect would have been anti-dilutive.

[2] For the six month periods ended November 30, 2012 and 2011, approximately 2,970,000 shares and 2,522,000 shares of stock, respectively, granted under stock-based compensation plans were excluded from the calculation of diluted EPS for those periods, as the effect would have been anti-dilutive.