Components of Total Equity and Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2013	Nov. 30, 2012	Nov. 30, 2013	Nov. 30, 2012
Stockholders Equity Note [Line Items]
Total equity, beginning of period	$ 1,423,727	$ 1,369,600	$ 1,354,933	$ 1,313,983
Net income	68,414	46,087	175,303	83,954
Other Comprehensive Income:
Foreign currency translation adjustments	24,205	(2,036)	10,791	37,194
Pension and other postretirement benefit liability adjustments, net of tax	2,211	3,378	5,135	4,584
Unrealized (loss) on securities, net of tax	6,401	2,076	4,962	1,724
Unrealized (loss) on derivatives, net of tax	(994)	(744)	(885)	(557)
Total Other Comprehensive Income	31,823	2,674	20,003	42,945
Total Comprehensive Income	100,237	48,761	195,306	126,899
Dividends paid	(31,960)	(29,773)	(61,796)	(58,054)
Other noncontrolling interest activity		(975)		309
Stock option exercises, net	261	1,762	2,662	2,365
Stock based compensation expense	773	623	1,482	1,211
Restricted awards, net	4,023	3,638	8,140	6,923
Total Equity, end of period	1,493,860	1,392,542	1,493,860	1,392,542
Shares repurchased	(6,867)	(1,094)		(1,094)
Total RPM International Inc. Equity
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,261,684	1,226,240	1,200,858	1,183,656
Net income	63,562	41,668	166,660	75,581
Other Comprehensive Income:
Foreign currency translation adjustments	19,409	(3,659)	2,338	25,005
Pension and other postretirement benefit liability adjustments, net of tax	2,200	3,242	4,961	4,776
Unrealized (loss) on securities, net of tax	6,341	1,865	4,909	2,690
Unrealized (loss) on derivatives, net of tax	(782)	(585)	(696)	(416)
Total Other Comprehensive Income	27,168	863	11,512	32,055
Total Comprehensive Income	90,730	42,531	178,172	107,636
Dividends paid	(31,960)	(29,773)	(61,796)	(58,054)
Other noncontrolling interest activity	(88)	(975)	(429)	309
Stock option exercises, net	261	1,762	2,662	2,365
Stock based compensation expense	773	623	1,482	1,211
Restricted awards, net	4,023	3,638	8,140	6,923
Total Equity, end of period	1,322,222	1,242,952	1,322,222	1,242,952
Shares repurchased	(6,867)	(1,094)		(1,094)
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Total equity, beginning of period	162,043	143,360	154,075	130,327
Net income	4,852	4,419	8,643	8,373
Other Comprehensive Income:
Foreign currency translation adjustments	4,796	1,623	8,453	12,189
Pension and other postretirement benefit liability adjustments, net of tax	11	136	174	(192)
Unrealized (loss) on securities, net of tax	60	211	53	(966)
Unrealized (loss) on derivatives, net of tax	(212)	(159)	(189)	(141)
Total Other Comprehensive Income	4,655	1,811	8,491	10,890
Total Comprehensive Income	9,507	6,230	17,134	19,263
Other noncontrolling interest activity	88		429
Total Equity, end of period	$ 171,638	$ 149,590	$ 171,638	$ 149,590