Components of Total Equity and Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2011	Nov. 30, 2010
Total equity, beginning of period	$ 1,435,737	$ 1,236,879	$ 1,387,368	$ 1,161,241
Net income	53,919	53,503	137,259	128,497
Other Comprehensive Income:
Foreign currency translation adjustments	(64,313)	20,046	(73,417)	45,402
Pension and other postretirement benefit liability adjustments, net of tax	3,181	1,514	5,399	2,150
Unrealized gain (loss) on securities, net of tax	(7,719)	2,540	(10,972)	8,234
Unrealized gain on derivatives, net of tax	(2,793)	996	(3,872)	3,843
Total Other Comprehensive Income, net of tax	(71,644)	25,096	(82,862)	59,629
Comprehensive Income	(17,725)	78,599	54,397	188,126
Dividends paid	(28,196)	(27,282)	(55,620)	(53,911)
Other noncontrolling interest activity	(1,603)	2,076		1,088
Other			(1,993)
Shares repurchased	(2,802)	(9,388)	(3,008)	(17,948)
Stock option exercises, net	1,975	2,184	3,181	2,614
Stock based compensation expense	3,567	540	6,692	6,027
Restricted awards, net	(2,926)	673	(2,990)	(2,956)
Total Equity, end of period	1,388,027	1,284,281	1,388,027	1,284,281
Total RPM International Inc. Equity
Total equity, beginning of period	1,304,339	1,141,637	1,263,164	1,079,473
Net income	49,931	48,791	126,742	117,787
Other Comprehensive Income:
Foreign currency translation adjustments	(60,471)	21,144	(69,904)	40,417
Pension and other postretirement benefit liability adjustments, net of tax	2,799	1,644	4,840	2,235
Unrealized gain (loss) on securities, net of tax	(9,323)	4,616	(12,966)	9,571
Unrealized gain on derivatives, net of tax	(2,196)	783	(3,044)	3,021
Total Other Comprehensive Income, net of tax	(69,191)	28,187	(81,074)	55,244
Comprehensive Income	(19,260)	76,978	45,668	173,031
Dividends paid	(28,196)	(27,282)	(55,620)	(53,911)
Other noncontrolling interest activity	(1,603)	2,076		1,088
Other			(1,993)
Shares repurchased	(2,802)	(9,388)	(3,008)	(17,948)
Stock option exercises, net	1,975	2,184	3,181	2,614
Stock based compensation expense	3,567	540	6,692	6,027
Restricted awards, net	(2,926)	673	(2,990)	(2,956)
Total Equity, end of period	1,255,094	1,187,418	1,255,094	1,187,418
Noncontrolling Interest
Total equity, beginning of period	131,398	95,242	124,204	81,768
Net income	3,988	4,712	10,517	10,710
Other Comprehensive Income:
Foreign currency translation adjustments	(3,842)	(1,098)	(3,513)	4,985
Pension and other postretirement benefit liability adjustments, net of tax	382	(130)	559	(85)
Unrealized gain (loss) on securities, net of tax	1,604	(2,076)	1,994	(1,337)
Unrealized gain on derivatives, net of tax	(597)	213	(828)	822
Total Other Comprehensive Income, net of tax	(2,453)	(3,091)	(1,788)	4,385
Comprehensive Income	1,535	1,621	8,729	15,095
Total Equity, end of period	$ 132,933	$ 96,863	$ 132,933	$ 96,863