Components of Total Equity and Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended
	Aug. 31, 2015	Aug. 31, 2014
Stockholders Equity Note [Line Items]
Total equity, beginning of period	$ 1,293,465	$ 1,578,594
Net income	100,362	104,839
Other Comprehensive Income:
Foreign currency translation adjustments	(30,606)	(21,266)
Pension and other postretirement benefit liability adjustments, net of tax	4,160	2,929
Unrealized (loss) gain on securities, net of tax	(7,084)	76
Unrealized gain on derivatives, net of tax		(66)
Total Other Comprehensive Income, net of tax	(33,530)	(18,327)
Comprehensive Income	66,832	86,512
Dividends paid	(34,634)	(31,987)
Shares repurchased and returned for taxes	(35,348)
Stock option exercises, net of shares returned for taxes		(4,451)
Stock based compensation expense	6,707	5,700
Total Equity, end of period	1,297,022	1,634,368
Total RPM International Inc. Equity
Stockholders Equity Note [Line Items]
Total equity, beginning of period	1,291,392	1,382,844
Net income	99,815	99,079
Other Comprehensive Income:
Foreign currency translation adjustments	(30,606)	(17,738)
Pension and other postretirement benefit liability adjustments, net of tax	4,160	2,760
Unrealized (loss) gain on securities, net of tax	(7,084)	83
Unrealized gain on derivatives, net of tax		(52)
Total Other Comprehensive Income, net of tax	(33,530)	(14,947)
Comprehensive Income	66,285	84,132
Dividends paid	(34,634)	(31,987)
Other noncontrolling interest activity		(4)
Shares repurchased and returned for taxes	(35,348)
Stock option exercises, net of shares returned for taxes		(4,451)
Stock based compensation expense	6,707	5,700
Total Equity, end of period	1,294,402	1,436,234
Noncontrolling Interest
Stockholders Equity Note [Line Items]
Total equity, beginning of period	2,073	195,750
Net income	547	5,760
Other Comprehensive Income:
Foreign currency translation adjustments		(3,528)
Pension and other postretirement benefit liability adjustments, net of tax		169
Unrealized (loss) gain on securities, net of tax		(7)
Unrealized gain on derivatives, net of tax		(14)
Total Other Comprehensive Income, net of tax		(3,380)
Comprehensive Income	547	2,380
Other noncontrolling interest activity		4
Total Equity, end of period	$ 2,620	$ 198,134