Reconciliation of Numerator and Denominator of Basic and Diluted Earnings Per Share, Calculated using Treasury Method and Two-Class Method (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Aug. 31, 2015	Aug. 31, 2014
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders		$ 99,815	$ 99,079
Less: Allocation of earnings and dividends to participating securities		(1,577)	(2,179)
Net income available to common shareholders - basic		98,238	96,900
Add: Undistributed earnings reallocated to unvested shareholders			12
Reverse allocation of earnings and dividends to participating securities		1,577
Add: Income effect of contingently issuable shares		1,356	1,339
Net income available to common shareholders - diluted		$ 101,171	$ 98,251
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		130,045	130,094
Average diluted options		2,360	1,065
Net issuable common share equivalents		1,023
Additional shares issuable assuming conversion of convertible securities	[1]	3,879	3,873
Total shares for diluted earnings per share		137,307	135,032
Earnings per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic		$ 0.76	$ 0.74
Diluted	[2]	$ 0.74	$ 0.73

[1] Represents the number of shares that would be issued if our contingently convertible notes were converted. We include these shares in the calculation of diluted EPS as the conversion of the notes may be settled, at our election, in cash, shares of our common stock, or a combination of cash and shares of our common stock.

[2] For the quarters ended August 31, 2015 and 2014, approximately 2,201,000 and 3,034,000 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.