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
	Aug. 31, 2013		Aug. 31, 2012
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders	$ 103,098		$ 33,913
Less: Allocation of earnings and dividends to participating securities	(2,285)		(642)
Net income available to common shareholders - basic	100,813		33,271
Add: Undistributed earnings reallocated to unvested shareholders	12		1
Net income available to common shareholders - diluted	$ 100,825		$ 33,272
Denominator for basic and diluted earnings per share:
Basic weighted average common shares	129,344		128,805
Average diluted options	950		765
Total shares for diluted earnings per share	130,294		129,570
Earnings Per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic	$ 0.78		$ 0.26
Diluted	$ 0.77	[1]	$ 0.26	[1]

[1] For the quarters ended August 31, 2013 and 2012, approximately 3,097,000 and 2,954,000 shares of stock, respectively, granted under stock-based compensation plans were excluded from the calculation of diluted earnings per share, as the effect would have been anti-dilutive.