Reconciliation of Numerator and Denominator of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Aug. 31, 2016	Aug. 31, 2015
Numerator for earnings per share:
Net income attributable to RPM International Inc. stockholders		$ 112,769	$ 99,815
Less: Allocation of earnings and dividends to participating securities		(1,819)	(1,577)
Net income available to common shareholders - basic		110,950	98,238
Add: Undistributed earnings reallocated to unvested shareholders		7
Reverse: Allocation of earnings and dividends to participating securities			1,577
Add: Income effect of contingently issuable shares		1,362	1,356
Net income available to common shareholders - diluted		$ 112,319	$ 101,171
Denominator for basic and diluted earnings per share:
Basic weighted average common shares		130,600	130,045
Average diluted options		749	3,383
Additional shares issuable assuming conversion of convertible securities	[1]	3,892	3,879
Total shares for diluted earnings per share		135,241	137,307
Earnings per Share of Common Stock Attributable to RPM International Inc. Stockholders:
Basic Earnings Per Share of Common Stock		$ 0.85	$ 0.76
Diluted Earnings Per Share of Common Stock		$ 0.83	$ 0.74

[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.