Components of Total Equity and Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Aug. 31, 2012	Aug. 31, 2011
Stockholders Equity Note [Line Items]
Total equity, beginning of period	$ 1,313,983	$ 1,387,368
Net income	37,867	83,340
Other Comprehensive Income:
Foreign currency translation adjustments	39,230	(9,104)
Pension and other postretirement benefit liability adjustments, net of tax	1,206	2,218
Unrealized gain (loss) on securities, net of tax	(352)	(3,253)
Unrealized gain on derivatives, net of tax	187	(1,079)
Total Other Comprehensive Income, net of tax	40,271	(11,218)
Comprehensive Income	78,138	72,122
Dividends paid	(28,281)	(27,424)
Other noncontrolling interest activity		(390)
Other	1,284
Shares repurchased		(206)
Stock option exercises, net	603	1,206
Stock based compensation expense	588	3,125
Restricted awards, net	3,285	(64)
Total Equity, end of period	1,369,600	1,435,737
Total RPM International Inc. Equity
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,183,656	1,263,164
Net income	33,913	76,811
Other Comprehensive Income:
Foreign currency translation adjustments	28,664	(9,433)
Pension and other postretirement benefit liability adjustments, net of tax	1,534	2,041
Unrealized gain (loss) on securities, net of tax	825	(3,643)
Unrealized gain on derivatives, net of tax	169	(848)
Total Other Comprehensive Income, net of tax	31,192	(11,883)
Comprehensive Income	65,105	64,928
Dividends paid	(28,281)	(27,424)
Other noncontrolling interest activity		(390)
Other	1,284
Shares repurchased		(206)
Stock option exercises, net	603	1,206
Stock based compensation expense	588	3,125
Restricted awards, net	3,285	(64)
Total Equity, end of period	1,226,240	1,304,339
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Total equity, beginning of period	130,327	124,204
Net income	3,954	6,529
Other Comprehensive Income:
Foreign currency translation adjustments	10,566	329
Pension and other postretirement benefit liability adjustments, net of tax	(328)	177
Unrealized gain (loss) on securities, net of tax	(1,177)	390
Unrealized gain on derivatives, net of tax	18	(231)
Total Other Comprehensive Income, net of tax	9,079	665
Comprehensive Income	13,033	7,194
Total Equity, end of period	$ 143,360	$ 131,398