Components of Total Equity and Comprehensive Income (Detail) (USD $) In Thousands	3 Months Ended
	Aug. 31, 2011	Aug. 31, 2010
Stockholders Equity Note [Line Items]
Total equity, beginning of period	$ 1,387,368	$ 1,161,241
Net income	83,340	74,994
Other Comprehensive Income:
Foreign currency translation adjustments	(9,104)	25,356
Pension and other postretirement benefit liability adjustments, net of tax	2,218	636
Unrealized gain (loss) on securities, net of tax	(3,253)	5,694
Unrealized gain on derivatives, net of tax	(1,079)	2,847
Total Other Comprehensive Income, net of tax	(11,218)	34,533
Comprehensive Income	72,122	109,527
Dividends paid	(27,424)	(26,629)
Other noncontrolling interest activity	(390)	(988)
Shares repurchased	(206)	(8,560)
Stock option exercises, net	1,206	428
Stock based compensation expense	3,125	2,396
Restricted awards, net	(64)	(536)
Total Equity, end of period	1,435,737	1,236,879
Total RPM International Inc. Equity
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,263,164	1,079,473
Net income	76,811	68,996
Other Comprehensive Income:
Foreign currency translation adjustments	(9,433)	19,273
Pension and other postretirement benefit liability adjustments, net of tax	2,041	591
Unrealized gain (loss) on securities, net of tax	(3,643)	4,955
Unrealized gain on derivatives, net of tax	(848)	2,238
Total Other Comprehensive Income, net of tax	(11,883)	27,057
Comprehensive Income	64,928	96,053
Dividends paid	(27,424)	(26,629)
Other noncontrolling interest activity	(390)	(988)
Shares repurchased	(206)	(8,560)
Stock option exercises, net	1,206	428
Stock based compensation expense	3,125	2,396
Restricted awards, net	(64)	(536)
Total Equity, end of period	1,304,339	1,141,637
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Total equity, beginning of period	124,204	81,768
Net income	6,529	5,998
Other Comprehensive Income:
Foreign currency translation adjustments	329	6,083
Pension and other postretirement benefit liability adjustments, net of tax	177	45
Unrealized gain (loss) on securities, net of tax	390	739
Unrealized gain on derivatives, net of tax	(231)	609
Total Other Comprehensive Income, net of tax	665	7,476
Comprehensive Income	7,194	13,474
Total Equity, end of period	$ 131,398	$ 95,242