Components of Total Equity and Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2012	Nov. 30, 2011	Nov. 30, 2012	Nov. 30, 2011
Stockholders Equity Note [Line Items]
Total equity, beginning of period	$ 1,369,600	$ 1,435,737	$ 1,313,983	$ 1,387,368
Net income	46,087	53,919	83,954	137,259
Other Comprehensive Income:
Foreign currency translation adjustments	(2,036)	(64,313)	37,194	(73,417)
Pension and other postretirement benefit liability adjustments, net of tax	3,378	3,181	4,584	5,399
Unrealized gain (loss) on securities, net of tax	2,076	(7,719)	1,724	(10,972)
Unrealized (loss) on derivatives, net of tax	(744)	(2,793)	(557)	(3,872)
Total Other Comprehensive Income, net of tax	2,674	(71,644)	42,945	(82,862)
Total Comprehensive Income	48,761	(17,725)	126,899	54,397
Dividends paid	(29,773)	(28,196)	(58,054)	(55,620)
Other noncontrolling interest activity	(973)	(1,603)	309	(1,993)
Shares repurchased	(835)	(5,728)	(1,094)	(5,998)
Stock option exercises, net	1,501	1,975	2,365	3,181
Stock based compensation expense	623	3,567	1,211	6,692
Restricted awards, net	3,638		6,923
Total Equity, end of period	1,392,542	1,388,027	1,392,542	1,388,027
Total RPM International Inc. Equity
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,226,240	1,304,339	1,183,656	1,263,164
Net income	41,668	49,931	75,581	126,742
Other Comprehensive Income:
Foreign currency translation adjustments	(3,659)	(60,471)	25,005	(69,904)
Pension and other postretirement benefit liability adjustments, net of tax	3,242	2,799	4,776	4,840
Unrealized gain (loss) on securities, net of tax	1,865	(9,323)	2,690	(12,966)
Unrealized (loss) on derivatives, net of tax	(585)	(2,196)	(416)	(3,044)
Total Other Comprehensive Income, net of tax	863	(69,191)	32,055	(81,074)
Total Comprehensive Income	42,531	(19,260)	107,636	45,668
Dividends paid	(29,773)	(28,196)	(58,054)	(55,620)
Other noncontrolling interest activity	(973)	(1,603)	309	(1,993)
Shares repurchased	(835)	(5,728)	(1,094)	(5,998)
Stock option exercises, net	1,501	1,975	2,365	3,181
Stock based compensation expense	623	3,567	1,211	6,692
Restricted awards, net	3,638		6,923
Total Equity, end of period	1,242,952	1,255,094	1,242,952	1,255,094
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Total equity, beginning of period	143,360	131,398	130,327	124,204
Net income	4,419	3,988	8,373	10,517
Other Comprehensive Income:
Foreign currency translation adjustments	1,623	(3,842)	12,189	(3,513)
Pension and other postretirement benefit liability adjustments, net of tax	136	382	(192)	559
Unrealized gain (loss) on securities, net of tax	211	1,604	(966)	1,994
Unrealized (loss) on derivatives, net of tax	(159)	(597)	(141)	(828)
Total Other Comprehensive Income, net of tax	1,811	(2,453)	10,890	(1,788)
Total Comprehensive Income	6,230	1,535	19,263	8,729
Total Equity, end of period	$ 149,590	$ 132,933	$ 149,590	$ 132,933