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, 2014		Nov. 30, 2013		Nov. 30, 2014		Nov. 30, 2013
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders	$ 69,766		$ 63,562		$ 168,845		$ 166,660
Less: Allocation of earnings and dividends to participating securities	(1,602)		(1,379)		(3,673)		(3,521)
Net income available to common shareholders - basic	68,164		62,183		165,172		163,139
Add: Undistributed earnings reallocated to unvested shareholders	6		6		18		17
Add: Income effect of contingently issuable shares	1,340				2,679
Net income available to common shareholders - diluted	$ 69,510		$ 62,189		$ 167,869		$ 163,156
Denominator for basic and diluted earnings per share:
Basic weighted average common shares	130,028		129,426		130,061		129,385
Average diluted options	1,063		992		1,064		974
Additional shares issuable assuming conversion of convertible securities	3,875				3,875
Total shares for diluted earnings per share	134,966	[1],[2]	130,418	[1],[2]	135,000	[1],[2]	130,359	[1],[2]
Earnings per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock	$ 0.52		$ 0.48		$ 1.27		$ 1.26
Diluted Earnings Per Share of Common Stock	$ 0.52		$ 0.48		$ 1.24		$ 1.25

[1] For the three month periods ended November 30, 2014 and 2013, respectively, approximately 3.2 million shares and 3.1 million shares of stock granted under stock-based compensation plans were excluded from the calculation of diluted EPS, as the effect would have been anti-dilutive.

[2] For the six month periods ended November 30, 2014 and 2013, respectively, approximately 3.0 million shares and 2.9 million shares of stock granted under stock-based compensation plans were excluded from the calculation of diluted EPS, as the effect would have been anti-dilutive.