Components of Total Equity and Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 29, 2012	Feb. 28, 2011	Feb. 29, 2012	Feb. 28, 2011
Total equity, beginning of period	$ 1,388,027	$ 1,284,281	$ 1,387,368	$ 1,161,241
Net income	7,924	1,193	145,183	129,690
Other Comprehensive Income:
Foreign currency translation adjustments	22,257	41,203	(51,160)	86,605
Pension and other postretirement benefit liability adjustments, net of tax	871	(275)	6,270	1,875
Unrealized gain (loss) on securities, net of tax	2,474	(3,381)	(8,498)	4,853
Unrealized gain on derivatives, net of tax	(793)	65	(4,665)	3,908
Total Other Comprehensive Income, net of tax	24,809	37,612	(58,053)	97,241
Comprehensive Income	32,733	38,805	87,130	226,931
Dividends paid	(28,251)	(27,278)	(83,871)	(81,189)
Other noncontrolling interest activity	1,118	3,068		4,156
Other			(875)
Shares repurchased			(3,008)	(17,948)
Stock option exercises, net	2,970	5,440	6,151	8,052
Stock based compensation expense	3,182	531	9,874	1,543
Restricted awards, net	(575)	1,823	(3,565)	3,884
Total Equity, end of period	1,399,204	1,306,670	1,399,204	1,306,670
Total RPM International Inc. Equity
Total equity, beginning of period	1,255,094	1,187,418	1,263,164	1,079,473
Net income	6,625	1,097	133,367	118,884
Other Comprehensive Income:
Foreign currency translation adjustments	24,083	44,038	(45,821)	84,455
Pension and other postretirement benefit liability adjustments, net of tax	983	54	5,823	2,289
Unrealized gain (loss) on securities, net of tax	3,592	(4,718)	(9,374)	4,853
Unrealized gain on derivatives, net of tax	(623)	51	(3,667)	3,072
Total Other Comprehensive Income, net of tax	28,035	39,425	(53,039)	94,669
Comprehensive Income	34,660	40,522	80,328	213,553
Dividends paid	(28,251)	(27,278)	(83,871)	(81,189)
Other noncontrolling interest activity	1,118	3,068		4,156
Other			(875)
Shares repurchased			(3,008)	(17,948)
Stock option exercises, net	2,970	5,440	6,151	8,052
Stock based compensation expense	3,182	531	9,874	1,543
Restricted awards, net	(575)	1,823	(3,565)	3,884
Total Equity, end of period	1,268,198	1,211,524	1,268,198	1,211,524
Noncontrolling Interest
Total equity, beginning of period	132,933	96,863	124,204	81,768
Net income	1,299	96	11,816	10,806
Other Comprehensive Income:
Foreign currency translation adjustments	(1,826)	(2,835)	(5,339)	2,150
Pension and other postretirement benefit liability adjustments, net of tax	(112)	(329)	447	(414)
Unrealized gain (loss) on securities, net of tax	(1,118)	1,337	876
Unrealized gain on derivatives, net of tax	(170)	14	(998)	836
Total Other Comprehensive Income, net of tax	(3,226)	(1,813)	(5,014)	2,572
Comprehensive Income	(1,927)	(1,717)	6,802	13,378
Total Equity, end of period	$ 131,006	$ 95,146	$ 131,006	$ 95,146