Reconciliation of the Numerator and Denominator of Basic and Diluted Earnings Per Share, Calculated using the Two-Class Method (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Nov. 30, 2011		Nov. 30, 2010		Nov. 30, 2011		Nov. 30, 2010
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders	$ 49,931		$ 48,791		$ 126,742		$ 117,787
Less: Allocation of earnings and dividends to participating securities	(979)		(830)		(2,297)		(1,712)
Net income available to common shareholders - basic	48,952		47,961		124,445		116,075
Add: Undistributed earnings reallocated to unvested shareholders	2		2		5		4
Net income available to common shareholders - diluted	$ 48,954		$ 47,963		$ 124,450		$ 116,079
Denominator for basic and diluted earnings per share:
Basic weighted average common shares	127,986		127,012		128,048		127,491
Average diluted options	446		658		489		559
Total shares for diluted earnings per share	128,432	[1],[2]	127,670	[1],[2]	128,537	[1],[2]	128,050	[1],[2]
Earnings per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock	$ 0.38		$ 0.38		$ 0.97		$ 0.91
Diluted Earnings Per Share of Common Stock	$ 0.38	[1],[2]	$ 0.38	[1],[2]	$ 0.97	[1],[2]	$ 0.91	[1],[2]

[1] For the quarters ended November 30, 2011 and 2010, approximately 2,722,000 and 2,197,000 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.

[2] For the six month periods ended November 30, 2011 and 2010, approximately 2,522,000 and 1,867,000 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.